What happens to your plumbing at 20 below?
Ever hear of indoor plumbing in your neck of the woods? 
The pipes inside the house don’t freeze because of the heat in the house (unless the heat fails or the pipes are not installed properly – it happened once to me because a pipe ran past a broken window in a basement closet).
The pipes to the house are deep enough in the ground so that they don’t freeze. The ground retains a certain amount of heat all year around, and you don’t have to go particularly deep to find a level where it’s above freezing year round.
When I was plumbing in Virginia the code said you had to wrap all pressurized lines in heat tape in mobile homes. This tape has a heating wire running through it, and gets connected to the electrical supply.
I am curious about connecting the home without a basement to the water supply.
Most people I’ve seen put in an insulated skirt around the bottom. The water line comes up through the cement pad, which I believe is pretty much required if you don’t have a basement under it. An auxiliary heater is occasionally used in the crawl space between the cement pad and the trailer. Usually though with an insulated skirt and enough warmth leaking out the bottom of the trailer and the occasional use of the water the pipes are pretty good at not freezing.
Your best bet is to find out how deep the frost line is and then bring it straight up into the trailer after going below the frost line for whatever horizontal maneuvering needs to be done from the well source. Between the ground and the bottom of the trailer try to surround the pipe with some insulating material. Even bales of hay would be helpful. During cold nights consider leaving the water dripping or very slowly running stream, just enough that the supply line has to refill the tank occasionally to keep things from freezing. I’ve always been worried about the use of heat tape after hearing it blamed for the occasional fire.
I know that if you are in an old house, you are told to leave the water in the tub trickling a bit to keep the flow of water coming, in order to stop the freezing. I’d assume the same could be attributed to mobile homes.