Oh, hi again.
This proposal is currently stuck. 
I know the current curves do not look very pretty. I am not updating those anytime soon because I’m lazy. But I think this is not really important. I may tackle it if the bigger problem has been solved.
The bigger problem where this is stuck is the question on how to put all the rail tiles onto the map. I have no real clue.
Someone suggested it could be done similar like the subway or even the river but I think this is non-sense. If railroads lead anywhere at least, then cities, of course. But I can’t just place a station into a city and connect dots. Problem #1 would be houses that are aligned to a railroad, because the railroad just blindly went over an ordinary road. Problem #2 would be the rail can possibly replace roads and therefore break the entire road network of the city. :-/ And there are probably other issues with that as well.
I have no real plan how to lay those railroads or how to make them “grow”.
Another question is: Where should railroad stations be placed? Yes, I also plan train stations. It could be just a dummy overmap tile at the beginning, and the railroad is forced to go along those tiles. Certainly railroad stations belong to cities. But I think they also should occasionally stop somewhere else, for flavor reasons. The question is where exactly and how?
That’s why you haven’t heard from this for some time now.