Interesting reading and it has my curiosity peaked. This is one of those situations that should be in the "10 to the minus 9 chance of probability" category so beloved of some of my FMEA colleagues. The five minutes of power remaining for the standby is quite normal in the case of a total electrical failure (FAR 25.1351), but (and this is the main question here) why didn't the RAT or whatever the Airbus equivalent is deploy to restore power? This seems to be a very strange combination of the aircraft apparently losing all power (only reason I can think of for all the displays to go dark) and yet not reverting to standby power automatically. Very strange.
I shall eagerly await the final report!
