I believe batteries and electric motors can replace almost all applications of gas engines. However, diesel engines still are a step too far now IMO. Most people have never operated a diesel engine. Their efficiency is very impressive. My 7,000 lbs truck with a Cummins diesel engine gets better MPGs than my partner's 4,000 lbs Mini Cooper Countryman.
Lots of idling. Lots of low RPM operation. Lots of stop and start wasting a lot of energy into the brakes.
A school bus is practically engineered to be an EV propaganda piece.