Tesla sideswipes and torches in Moscow.
If this can occur with an electric car cannot it also happen to an electric bus? Of course you would want to know precisely the train of events but clearly fire is a danger with these batteries.
A couple of questions come to mind: (1) How much of the volume and weight of an electric bus is taken up with the batteries and (2) how fast and explosive are these fires?
Seems to me a combo trolley and battery bus would be safer as the current storage unit should be smaller and less "optimized".