The reports I read said this was an older installation - was that one setup in the same way as a modern plant would be done? That is to say - was there anything unique about this failure scenario?

The pictures I saw was that the Moss batteries were located inside a building. My mental image of battery storage is freight-sized containers offset from each other - presumably to minimize fire risk. Or was this plant a common dense configuration that is done in areas where they are heavily space constrained?