Maybe this is relevant, maybe this isn't relevant. But Nat made a tow truck out of a schoolbus. which you can find here
Since commercial vehicles can weigh 26,000lbs, my ignorant self would weigh the bus and if it was under 16,000lbs and the trailer weighed less than 10,000lbs. I'd probably tow up to 100 miles if necessity arose. However I would probably do this before making the bus awesome. My halfassed logic doesn't factor in any actual mechanics though, which is probably far more important than rules and laws.