More of my
Without a proper dispatcher screen, hierarchical multiplayer a la Run8 probably won't be possible.
Perhaps multiplayer like in Farming Simulator, where one player hosts his game in server mode and invites the public or friends only to join the game.
In FS you driver your tractor, harvester, etc. independently over the roads obeying traffic rules, or work the fields as a team.
In TSW one player hosts his game in server mode, starts a scenario with trains at designated locations with specific routing and tasks pre-programmed (since trains aren't free roaming road vehicles) and invites the public or private friends to take control of one of the trains. A good computerised dispatching/interlocking can prevent clashes, collisions and stand-offs. I think the ideal multiplayer route isn't that big, not bigger than Cajon Sub, but Tehachapi Pass would do also.
Running past a red signal, fouling other train's paths or making a mess of the assigned tasks (like leaving cars on the mainline, failing to re-align switches, etc.) means you get a warning or even a penalty such as removal from the server, blocking of your username, etc.
It could just work, but certainly depends a lot on good will and a certain skill level of all involved.
A scoring/rating system would certainly help in separating the good, the bad and the ugly.
Like Buzz, I think too a scenario shouldn't last more than 60-90 minutes, and if you quit before the end, your train will take off into space. Relinquishing abandoned trains like in Run8 is also possible if the train is in a siding or otherwise out of the way.
If it is sensible to pause and resume play? Don't know.
Multiplayer is certainly an interesting prospect. Let's hope it brings a more intelligent dispatcher for AI trains.