The Class B license in California is what is necessary when operating a Coach 40 feet and larger, as well as over 22,000 lbs.
Not exactly Gary. The CA vehicle specifically indicates an RV (called a "house car" in CA) 40 feet or less can be operated with a Class C license. It does not matter if it's over 22,000 pounds.

The 22,000 limit applies to vehicles OTHER than RV's, like trucks, etc.

So, with a class C a 40 ft Prevost is legal. A 45 is not.

Ray