normally when the small earth cable is not put on or loose the car wont run start i've done that a few times after a big strip down as easy to do but it dont fire the car,,, but that said if there was a short circuit somewhere else and had no fuse in line could catch on fire, lot of car fires are due to fuel leaks or main battery leads getting damage on the positive side to deck, this will also make the battery explode and the gasses from the batter will catch fire and spray battery acid in to the air ir its a wet type .,
this all said it was done when booked in to a garage a garage must have insurance for this kind of thing including if some vandal attacks it etc, if they become a pain about remind them it was in their charge at the time etc,, contact your insutance company tell them whats happened if garage are being awkward about it,,, end of day its their liability and they must do right by you no court or judge would rule any other way,, trading standards could be a good port of call to help pressure them if needs be etc.
this all said it was done when booked in to a garage a garage must have insurance for this kind of thing including if some vandal attacks it etc, if they become a pain about remind them it was in their charge at the time etc,, contact your insutance company tell them whats happened if garage are being awkward about it,,, end of day its their liability and they must do right by you no court or judge would rule any other way,, trading standards could be a good port of call to help pressure them if needs be etc.
