If this is not a mobile dwelling I do not see how HUD can regulate it and I am not sure the "first responder" vehicle is legally required to be inspected although I can see why the government's insurance carrier might want it.
I inspected a trailer IBM set up to display a small computer system but it was acting as the IBM Installation Planning Rep, not as an electrical inspector and this thing traveled all over the country. I never heard of any problems. It was set up to plug into a garden variety 50a RV post. (actually 2 for the full boat load) Internally there were 2 50a panels, one for the house loads and one for the computer system.
This had no "living" facilities (plumbing or sleeping area) so they dodged HUD. Actually, unless the rules have recently changed, RVs are not HUD regulated either.
My son in law had a trailer that was really a house on wheels but it was titled as an RV and was not HUD certified.
These guys
http://www.nationalcabinsales.com/ but they called themselves Stewart Lodges then.
