Little Bill,
My RV is highly modified to withstand cold. Look at the full time forum where I have posted the upgrades I've made. On my maiden trip, the pex water hoses froze, and it was not particularly cold.
I agree rv use in extreme cold is somewhat rare, however I know of two other RV'ers who have managed to boondock at -40 (and not just one night), so it may not be as unusual after all. I've missed my chance to join the -40 club this year.