mxracin. There are a couple of other ideas for heating the waste tanks. Definately enclose them and insulate the enclosure. Some motorhomes run a heat duct from the regular furnace.

Since it would be a diesel truck go with a Aquahot or Hydrohot system. They use a diesel burner and you can put multiple zone heaters in the cabin, and storage compartments or the waste tank compartment.

A propane based system I also thought of was have a smaller propane furnace directed to the storage, waste tank area. In Colorado in the winter if it is not to cold and the sun is out you don't always have to run the coach furnace because the sun warms the coach through the windows. But the enclosed areas may still be cold. Pickup slide in campers have small furnaces. So add a small furnace directly to the tank area. Will probably use less propane than the regular furnace.

While driving it is not a problem because small auxiliary furnaces, hooked to the engine coolant are esily available.