In my previous job a few years back I did a lot of development and reliabiltiy engineering on an EV, many of which are in use across the UK.
We did some training sessions with Fire Crews and the reccomended procedures were to bascially move everybody away, then continually soak the packs to keep them cool, checking surface temperature regularly with a laser thermometer.
There have been a number of fires, and I know in at least one case, that the packs re-ignited whilst the vehicle was on the back of a wrecker in a recovery yard, many hours after having been dealt with.
What I will say – it doesn’t scare me at all – as it takes a LONG time for the fire to become uncontrolled or dangerous and you will know about it a long time before (through the vehicle systems and warnings or performance of the vehicle.).
Contrast that to Petrol cars which I have seen catch fire – including once which went from ‘ooh whats that smell’ to ‘rolling out the door of a roaring inferno’ in the time it takes to get from the outside lane to the hard shoulder.