A vast quantity of people and goods come through the ports every day, and as such a general strike by the Amalgamated Union of Dockworkers, Railwaymen and Ferrymen would spell disaster for the city. The first (and only, so far) time this happened was towards the beginning of the Last War, and whilst the Imperial Legions swiftly and ruthlessly crushed the strike it still caused enough disruption to throw the Emperor's war plans into disarray.
It's unlikely, however, that a general strike would ever come to pass. The rules of the Union state that for a strike to be called the Dockworkers', Railwaymen's and Ferrymen's Divisions each have to vote in favour. When things are bad for the docks they tend to be good for the railways, and the ferrymen are never especially keen to strike (and indeed are only in the Union for historical reasons, the Union having grown from the old Guild of Ferrymen - but because the taxi drivers have joined the Ferrymen Division, it has swollen vastly and is once again relevant in Union politics). The wartime alliance which was intended to strengthen the union has ended up reducing its credibility.
More common are strikes carried out by a particular section of the Union: the Dockworkers, perhaps, or the taxi drivers. This is far more easy for the authorities to deal with. When the dockworkers go on strike, the railwaymen all cheer because it means they get overtime pay, thanks to the extra goods trains. When the railwaymen go on strike, the dockworkers take up the slack with outgoing goods and the taxi drivers get more passengers. And when the taxi drivers go on strike, trade is barely disrupted. It's still a mess - after all, all those incoming ships and trains still have to be dealt with, and when the taxis aren't running the Order's rental charges become a train on the City's finances - but it's a managable mess.
I think it would make sense to have some sort of big terminus linking up to some sort of international train network with vast trains chugging along through the wilderness and being attacked by bandits, so I've put it in the docks.
Taxis: The devastation wreaked by the end of the Last War meant all the streets of the city had to be re-paved. This provided an opportunity: the Grey Order had produced wonderful steam-and-clockwork powered horseless carriages which chug along marvellously so long as there are special grooves on the streets to guide them. The Taxis do not go into the slums, but most other districts have at least a certain amount of coverage - in general, districts which are either well-off (like the noble quarter) or have a lot of places that people are liable to want to take taxis to (like the craftsman's quarter or the government district) have better taxi coverage than those that don't.
Although many rumours circulate to the contrary, the Order hasn't inscribed spyrunes in the taxis. The Order is sensible enough to realise that the Horizon authorities would subject the taxis to close scrutiny and would simply end the taxi contract if they discovered such meddling, and the sheer amount of paperwork such a vast number of spyrunes would require to administrate is excessive for the comparatively small amount of useful information that would be gleaned.
The terms of the taxi contract are slanted very slightly in favour of the Horizon government: part of the intent of the contract was to convince the authorities to allow the Grey Order to operate openly in Horizon, and although it turns a small profit the main benefit to the Grey Order is still diplomatic. The Horizon government also gives generous terms to the taxi drivers who rent taxis from them: when they have charged excessive rates the taxi drivers have been known to break down their taxis, sell the parts for scrap, and then claim that their taxi was hijacked and stolen. Of course, this definitely isn't (read: definitely is) encouraged by the Ferrymen's Division whenever relations with the authorities breaks down.
Thanks to the decent price an cars the Horizon government is able to get, the government has managed to maintain a small carpool, which is used by government agents. Private cars are extremely rare: wings are much more fashionable as far as fashion statements go.
The Steam Union denies absolutely all rumours that groups of Union heavies have been known to smash up taxis with big heavy spanners, and the Clockwork Guild knows nothing about the small clockwork hedgehogs some clever tinker's made which are designed to sit in the grooves and derail the taxis.
Wings: Clockwork metal wings, complete with a control glove which responds to minute movements of the right hand, are the status symbol of the rich and powerful. Many models are available in a variety of styles - large feathery wings for benign philanthropists, frightening bat wings for those who simply must look frightening and diabolical, garishly painted gossamer wings for fashion victims...
One mustn't leave one's wings unattended on the street for long, mind. They'll get stolen: wing-theft is common, mainly because the target of the theft is also a handy getaway vehicle.
Sabotage of a man's wings is very, very wrong. Simply pulling out a gear or two will prevent them from functioning. A man who knows his clockwork will know how to muck about with the landing mechanism, so that the wearer of the wings will not know that their transportation has been sabotaged until they are about to dive down hundreds of feet to land daintily in the street. It's always comical when things go wrong with that...
Brother Rufus and his men: Once upon a time the Emperor introduced crocodiles to the sewers of Horizon to bolster the defences against individuals crossing the Wall. Those crocodiles became ever-more crafty and wise, and Brother Rufus is now the leader of their tribe, a clique of talking intelligent crocodiles.
The Dockworker's Division pays Brother Rufus protection (in the form of big tasty slabs of meat) to stop him sending his boys to attack shipping. Brother Rufus is also willing to help guide people through the Wall in return for books, information, stories, and other forms of wisdom. Brother Rufus ultimately wants to learn magic so he can transform himself - or have someone transform him - into a dragon. Brother Rufus has high hopes and beautiful dreams. He is a living example of what happens when a crocodile pursues the path to ascension.
Grey Order safe houses: The Grey Order maintains three houses scattered around the docks. Sometimes, even the usual Order chapterhouses aren't secure enough: for example, when they have stolen something the Steam Union or the Clockworker's Guild are willing to invade the chapterhouse to get back, or when they need to smuggle a defector from the Union or the Guild out of Horizon. This is when the safe houses come in handy.