If anything an EV should be possible to design to be safer against fires, as it's the battery itself that burns. A metal fire break on the floor and a gap between that and the battery should give warning signs (smoke coming out the sides) and give people time to evacuate before it becomes too serious. Temperature sensors throughout the battery could give warning signs even before it gets to that.

In an ICE vehicle it's the vapour of the fuel that burns. The engine of buses/coaches is typically under the floor, with access panels, so vapour can easily get into the cabin.