I suspect there may be a strong correlation between incidences of EV's "going up" & the energy density of the pack, plus the rate of charge.The legislation will arrive.....shortly after there is some sort of terrible fire which causes great embarrassment and requires people be seen to act I reckon!
Regardless of the frequency of fires vs the number of vehicles etc...I find the risk of a self sustaining fire in a family car not acceptable. Theres enough evidence already to suggest there is a serious safety issue I think that needs to be addressed.
It's reasonable to think a high-end, high-performance EV might represent a higher risk than a commuter model with more modest output & pack.
No doubt the very well-paid Actuaries that calculate Risk for the Insurance Industry will answer that one for us in due course.