Commissary or freight house both make sense given the location. As does a company stores depot.
However, I KNOW that I just read something that should have the answer. The PRR T&HS have recently talked about that area (generally, WRT the shaft coming down). Take a look through their recent publications and see if you can find it. I wish I could be more specific, but, well, they're pretty lame at getting info on the web.
