Regarding the propane, In my home I used to have a propane fireplace. We had a 500gallon tank for it, and in one winter we would easily burn that propane just running the fireplace(and that was only when someone was in the basement so not really THAT much). I got rid of it for an electric fireplace instead.

The one shown in that picture is probably 1000 gallon, so this isn't that odd.
I HIGHLY doubt they're running generators on propane, but it's possible that they don't know how fast it is consumed.
I've been working at a sort of survival compound for a wealthy individual and we were recently discussing whether to run his backup generators on propane or natural gas, and he was set on propane. I told him I'd go with natural gas as propane is a by-product of oil refining.
Just my thoughts.