Bahnhoff is the subject here, because of the verb is (to be). Think of it like this. "It" is the subject and "it" is also "the station" they are the same thing so the have the same case.
There a only a few verbs in german where there can be two nominative Nouns, sein, heißen, bleiben und werden are the commonest and all fit with the "are the same thing" explanation.
I remember reading somewhere years ago that in some languages there is a strong contrast between "this" and "that", whatever this and that might be in the language. In other languages the contrast is less strong. I'm guessing that German-speakers use "das" and "dies" interchangeably to indicate something - provided that that something isn't far away - so that it's "Das ist ..." "Dies ist ..." whichever the speaker feels like using.
If the object is far away I think German-speakers would say "Das ist ..." There is a German word "jener/jene/jenes" which means "that", and that's the word in German that has a strong contrast with "dieser/diese/dieses", "this". ("Jener" is easy for English-speakers to remember as it's cognate with "yon" and "yonder".) However, despite the existence of this word, Google Translate suggests "Das da drueben ist ..." if you want to say "That thing over there is ..." Can anyone explain further?