When it comes to extinguishing fire, you play the cards you have to mitigate the situation. If what you have is a residential fire hydrant system that can supply 36,000 gallons, you use water in overwhelming force. As evidenced by the article, it will not quell the reaction but it will dampen the overall thermal situation enough to permit humans to be extracted safely.
Presumably it would have been better to dump a few thousand pounds of sand on it but there are few sand hydrants in USA residential neighborhoods.
What is though? My first thought was halon gas but I think you still have outrageously hot temperatures in the cells that will reignite after the halon has dissipated.
Put a large bell jar over the car and then pump out all the air? Or maybe pump liquid silicone into the battery compartment? (The theory there is you need a flame-retardant 'foam' at very high temp but you could submerge the battery compartment in...something like silicone, to isolate it from atmosphere; there would be heat as the batteries discharge, but no combustion.
