I agree with Kadeton, really. But i feel that the organisations probably are a little more fluid, with the captains being able to requisition across departments reasonably easier than it is in the modern world.
So you have the Governor and his primary police force, the Guild Guards. I feel that these guys can range from the worse guards up to some impressive shows of police power like the Riflemen.
The departments are mostly self explanatory, but while they have overt themes, i feel they have subtle themes with them too.
The Death Marshals are undead hunters, but i feel that they have a strong detective feel to them. The Death Marshal wagon is being called out to murders in which undead are felt to be involved and they investigate before direct pursuit.
The Witchling Stalkers are Arcanist Hunters, so destroyers of magic, but have a strong inquisition theme. They will take everything from you and force you to act how they like. Corruption and hypocrisy is strong and they are less about investigation of arcanists, more like directly taking them out or capturing them and turning them to witchlings behind closed doors.
The Ortegas are Neverborn Hunters, but they are also really focused on their ignorance. They know how to kill neverborn very well, but they generally do not try to know anything about them. This might be with the exception of Perdita, who after the Event seems to have picked up some insider knowledge. Perhaps an analog of 'things man was not meant to know'.
The Mechanical Section i feel arent like tanks, as Kadeton believes, but more related to cyberpunk and the governmental suppression of body modification, while using its technology to its own benefit. Probably the least corrupt of the organisations, though, due to its very small living body count.
I don't know as much about McCabe and friends, but i feel it is focusing on Corruption and criminality as an overt theme rather than the undercurrent which is in all the other departments. The Secret police hiring criminals.
I feel that these themes are great, if there was a Malifaux II then i would love for these themes to be expressed strongly in the mechanics, not just the fluff. But mostly its done amazingly already.