Very nice, thanks for the write up :). I was thinking about how you could get route maps, without actually having to source shape files. Given you are tracking trains every minute, you could probably build up your own route maps by dropping a point every time you get one, and connecting them with straight lines. Over time the route would become closer and closer to reality.
I did a quick write up about it here: https://rydercalmdown.com/projects/trains-fyi/
The hardest part was learning about GTFS-RT, which was a data format I wasn't familiar with until now.