Not only you don't need a GNSS to determine a fixed in place railroad station but actually you don't want to use a GNSS to do that.
A simple radio beacon working on ~400MHz is more than enough to solve this difficult technical obstacle.
Of course, this is totally ignoring what the trains do already know where they are because they need to display the current/next stations on the passenger information displays.
Kids these days...
Not only you don't need a GNSS to determine a fixed in place railroad station but actually you don't want to use a GNSS to do that.
A simple radio beacon working on ~400MHz is more than enough to solve this difficult technical obstacle.
Of course, this is totally ignoring what the trains do already know where they are because they need to display the current/next stations on the passenger information displays.