The way you put out a battery fire is you don't. Last I checked, the current best practice for an electric car that catches fire is to just let it burn to the ground while trying to stop anything around from catching fire.
Not to be callous but the "just let it burn to the ground while trying to stop anything around from catching fire." might be the structure over the basement in this case and the keeping other things from burning would be the surrounding buildings.
If firefighters can't access the basement safely, that's exactly what they'll do. They'll protect the exposures instead, ie the neighbouring buildings.
