That was exactly what I was thinking when it came to the subway system and the mob XD The subway I've considered to be something that was created a long time ago and doesn't get repaired often given it's location. It's rather dangerous to traverse on due to who travels on it and when it breaks down, that section of the track is usually down for months. Kinda like New York in the 1980s haha.
That being said, I can see parts of the track heading to the Middle and Upper Plate. These portions become more of a train than a subway system, similar to when the subways exit far enough out of Manhattan in present day New York, except quite the opposite. These portions would probably be well maintained, run smoothly and silently considering the technology jump, and be virtually safe to ride on, even at night.
But yeah, it'd definitely be something of a bonus to the Lower Plate given that if I wanted to go from MetroTech Park in Brooklyn to Washington Square in Manhattan, I'd take a 30 minute subway ride compared to a 2 hour walk XD If like described above, however, it'd be much more of a boon to the Upper and Middle Plates since a lot of people would probably stray away from it in the Lower Plate to prevent say...getting mugged, murdered, or even to avoid the congestion.
The mob thing...eh, I'll wait on the verdict of that before going into it. I can see either competing factions or a syndicate similar to what happened New York in the 1920's or 1930's respectively.