Please do not go under, or let anyone go under your coach unless it is blocked up at the chassis support points. When you are towed there are only two critical issues. First, make sure the tow truck has enough reach to get at the lift point(s) and still be capable of a sharp turn. If the reach on the truck is inadequate, send him away.
The second thing is pull the axle(s). Pulling them both is good insurance, but you can just do one. The tow truck driver should be able to pull and axle in 5 or 10 minutes it he has an impact wrench. Then you need a piece of carboard to cover the opening in the hub, or the driver should have the plastic caps to prevent loss of differential fluid. You are going to spill some grease but a cup under the axle flange prior to popping it out minimizes the mess and cleanup.
Do not let anyone tow your coach without pulling the axles or removing the driveshaft (not the easiest thing to do).
If the problem requires the bus being hauled on a flat bed trailer, you are at great risk of body damage. You may have to raise the front or rear ends or both, and then you still may not clear at the front or in the middle. If that occurs use blocking or whatever is needed to keep the chassis from dragging or hitting anything as it is loaded on the flat bed. Especially do not allow a tow truck driver in a hurry to push you around, He has no skin in the game and he could care less about your coach.