I remember reading instructions for the interchange of the through sleeper between Union Station and Dearborn Station in Chicago. The car WAS occupied. The instructions carried remarks that he car was to be handled with a minimum of discomfort to the passengers.
It's been quite a while, but if I recall correctly the eastbound move was handled by a Santa Fe crew and locomotive while the westbound move was handled by the Pennsy. Another through sleeper operated at one time via the New York Central and Santa Fe railroads.