I think it is a stock MTH item. It is customary for a dealer ship to obtain a fleet order for state police vehicles, along with city, town, fleets for public works trucks, and other fleet vehicles one can think of . There dealership logo would appear but not on the auto carrier itself. The vehicles would be picked up at the manufactures plant. I never heard of any dealership regardless of how large having their own auto carriers...
The only exception I can think of is if the dealership contracted a carrier company exclusively and required the carrier company to have the dealership name on the carrier...