So it turns out simutrans still is alive and slowly progressing. There's a new branch called simutrans experimental but I haven't fiddled with it much. Highlights of latest versions is the new sectional view and full Z levels for subways (and curved tunnels).
What is simutrans: Simutrans is an open source project dedicated to creating a transport simulator game in the spirit of transport tycoon, but with some different approaches and gameplay features, such as:
1: Full map pathfinding: each passanger in your vehicles has a destination and will pathfind trough your network to reach it (akin to cargodist experimentals on OTTD, but way better), no need to set "transfer" orders or whatever, the game figures out a path and gets the goods flowing
2: Modular cargo: A "peice goods" trailer can accept any good that is classfied as peice goods (such as electronics, plastics, finished goods, wool, etc), what allows for double-direction routes where your train hauls different stuff on each pass.
3: No breakdowns - simutrans is all about logistics, so no breakdowns or scheduled maintenance. You can also keep using obsolete stuff if they feel a niche you need.
4: Programable game speed - you can have the historical timeline progress super slowly, income rates and maintenance adjust themselves accordingly.
5: Full Z-levels above and underground: The UI is a bit unweildy but it works. Pics on the spoilers.
6: Brutal economics: turning a profit is hard, but you can reach the bill gates point in mid game, but in early game a network flop and you can go straight to bankrupticy.
7: Eletrification and passanger bonuses: You can build powerlines to take energy from powerplants to factories boosting their productivity.
8: Multiple content sets: Simutrans comes with paksets with different graphics styles and gameplay balance. The most popular paks are pak 64 and pak128 (the one used in my screenshots). You can mix-and-match content that is made for a given resolution for addons.
9: Per-block pathfinding: Trains only move if they can secure a route to the next signal or stop, so nothing crashes (even if they do, no breakdown, the line only clogs). That also means the train pathfinding is usually smarter. Same applies to ships, they can figure out a route on a complex maze without problem.
10: Emergent behaivour: You'll find cargo taking unexpected routes once your network gets complex enough. Same for passengers.
Bonus feature: Awful graphics! (But I supposed this shouldn't be a problem for the DF people).
tl;dr: Dorf fortress of transport tycoon genre.
Screenshots:
Crowded airport - multiple runways because the game's airplane code is still a bit herp.
Curved multi-level tunnel!
Subway on a crowded city.
Above-ground Z level demonstration on a double-decker station. Didn't have space on the side for a new platform, so I went up instead!