Yes...the driver dorms are a real 'throwback' to the early days (1920's -1960's) of Greyhound history, when many of the old art-deco terminal's had driver dorms built in, usually on the second floor....shades of the even older 'Railroad YMCA' dorms located in many railroad yards and stations for train crews...
The two level dorm in the former (now MTA) Greyhound garage basement, was perhaps one of, if not the last one built (1968). When the old Greyhound Corporation divested the bus line, much of the expensive real estate was not included. Since the MTA acquired it from the corporation, they had no use for the dorm, and it could not be easily converted into any other use for them, so they leased it to GL, and it was a good deal for all.
I wonder how many other dorms are still in use around the Greyhound system?