Down home.... from personal experience I don't believe the power of the Volvo engine is inadequate. Certainly a fire can happen as there are a lot of components that could fail as with any coach. Newer Prevosts have a built-in fire suppression system in the engine compartment with a warning and controller at the driver area.
The Volvo engine has 500 hp with 1,750 lb. ft of torque, not too shabby! The Detroit Diesel has 515-525 hp with 1,650 lb. ft. of torque.
You cannot upgrade the engine in a Prevost. There is not enough room for a larger engine.
Sounds like 'fire-side' chat.
Safe travels,
Mark