OK, fine, it may be true that all states except NJ allow for propane to be turned on and in use. However, unless the person who wrote that frozen food trucks use propane fired refrigeration is a driver, I would bet most of them are Freon based and run by electric!
The comment about motor homes running the furnace to heat the rigs while traveling, From what I've seen at shows, most A's use a hot water circulation system off the engine same as a car.
No matter what the case, I won't travel with the refrigerator, or the furnace running and the propane open. I've had two very close friends killed by a propane explosion and I care not to join them!
Bandaid