I've never been a CM so I don't know the layout, but I think this is how the building is structured:
View attachment 835383
Yellow shade is the train tunnel (indicated by the vents on top), the red shade is the diorama, and the green shades are offices/admin/etc.
Rereading what
@Old Mouseketeer wrote again, I believe I misinterpreted what they were saying and thought they were referring to another building deeper into the park, but actually meant the northern green area I've indicated. For that I deeply apologize for my defensiveness and misunderstanding.