One commentor said "I drove past it when only the wheel was on fire so it wasn't the cars" which may be true, I'm sure they'll the determine the source.
TBH I am surprised they put it out as fast as they did, maybe all the cars batteries didn't fully combust as it was out by 10:30am and started just before 6.30am. Either way, I am glad no one was hurt, it is a real shame when accidents like this occur regardless of the vehicles involved.
If it were ATTO 3's I don't thing they have NMC packs, only LFP, so perhaps the transporter was the route cause, as the BYD blade packs are very good at with standing high temperatures.