It looks to me like 50 Mass Ave. NE is actually located physically inside DC Union Station -- am I mistaken? I'd think they'd stay in touch with the situation on the ground in the station which they are *actually working inside*.... they don't even have to cross the street...
Amtrak management concerned with the situation on the ground at Union Station or operations in general are not located inside Union Station. All the offices for the terminal and the operations center for Washington Terminal are in another building.
I work for a big corporation.
My official work snailmail address is the company HQ. But in reality I'm not in the HQ building (and hardly ever even go there) but have my office in a smaller building more than a block away. The internal mailman brings me the mail there. But we still use the snailmail address of the HQ building. Maybe for prestige and recognition reasons? Maybe because its simpler to organize the mail that way? I don't know why. The only downside is that visitors don't always understand this and come to the wrong building, so I spend a lot of time giving directions to people.
Maybe it's similar with Amtrak.