Wouldn’t it come down to wattage rather than straight voltage?
My guess is even if the voltage is ramped back up (which does sound accurate), that voltage would droop quickly if anything tried to draw power from it. Probably still not a fun time for anyone on the lines, but Tesla coils go up to something like 20kV and I got shocked by those back in high school. It fucking hurts (actually, more like extreme discomfort) but isn’t fatal.
Not that I’m saying a generator or battery at 20kV is the same thing as a 20kV static discharge, just saying that even extreme voltages can be ok. It’s about the amperage, not the voltage. Would a home generator or car battery have the amperage if ramped up to thousands of volts, especially considering the whole point of the ramp up is to reduce the amperage to increase efficiency.
I’d also figure, unless the outage was just one house disconnected from the grid, wouldn’t any generator or battery end up powering the whole neighborhood and quickly overloading if it tried to send power back out to the grid?