Well, one way to look at it is fuel is a very dense battery. 1 liter of diesel has about 10kWh. 2 gallons of the stuff has as much stored energy as a fully charged Tesla Model S.
I think as battery storage gets denser these fires will become more common. Because there is just so much energy packed into such a small package.
I suppose shorts are easier to cause by physical breaching than fire by introduction of spark (e.g. you can puncture a gas tank and still not have it burst into flames without ignition).
But on the other hand, I'd assume the majority of car fires are caused by either fuel or oil lines into the engine being punctured and leaking around something hot enough to ignite them. Over a longer maintenance period (10 years+), I'd still bet on insulation over physical containment of a pumped liquid.
I think as battery storage gets denser these fires will become more common. Because there is just so much energy packed into such a small package.