Yes, where they are parked next to each other. One such scenario in the USA is where the guy had an accelerant repair job done on his vehicle and the consequent fire quickly caught on to other vehicles. There is always an exceptional reason for something to seemingly self-combust within seconds. According to the car parking document, it takes at least 300 seconds (five minutes) for a near-fully burning vehicle to cause a car parked next to it to successfully ignite. The guy in the CCTV wasn't parked next to anyone so in order to radiate heat towards other vehicles to cause spontaneous ignition needs it to heat to circa 500 °C IIRC. Yet the fire brigade were there within minutes and the guy was present when the fire started, although it might have taken him a while before he noticed it. Given the appearance of the flames in the CCTV and the white/grey appearance of the flames and smoke and its location, there is nothing at all unreasonable in the fire being identified as a lithium-ion one given such a fire burns at a MUCH higher temperature than diesel fuel or flame-resistant complex plastics.
I will wait for September for the facts, not some 'it is believed'-type opinion.
Again, where did you get September?
If a car can be burning like the BMW or Audi in the previously linked videos in about five minutes, then it doesn't need to be parked directly adjacent to another vehicle to ignite it. Said videos showed cars burning in the open, while the Range Rover in Luton was under a low ceiling, which trapped heat energy and diverted it to the sides, while also allowing fresh airflow to feed the fire through the open sides of the structure. And, as you already conceded, when the fuel tank ruptures, the burning fuel will run down slope. (You even suggested a containment system, presumably like a gutter, which is a really bad idea because it's still going to be directing burning fuel through the building.)
I know I'm not the only one to have called ******** on your "there within minutes" claim. You have not justified this claim, and you know it. That's why you make the vague statement "within minutes", allowing the reader to infer a very short time without actually committing to saying how long, because, after all, "within minutes" could mean fifteen minutes just as easily as three minutes. You also continue to make the ignorant assumption that the fire service drove straight to the parking garage, immediately turned their enormous, critical asset of a pumper truck up the ramp, and speed straight to the burning car to begin dousing it with copious amounts of water, all "within minutes" of the emergency call being received. That's ludicrous.
You have a habit of searching for numbers a posteriori, and when you think you find one you post it as though you actually know what you're talking about. You remind me of other conspiracy theorists who crow that spacecraft in low earth orbit would have to endure the 2,500 °C temperature of the thermosphere without understanding the difference between heat and temperature.