Joesoap------The A330 RAT will provide 3.5 kva if required via the Emerg Gen. Not a lot but enough to get you down ASAP with no Eng/Apu Gen or Green Hyd power for the Emerg Gen.
So in the Airbus if you lose Both Eng Gens and the Apu Gen you still have the Emerg Gen available at either 8.6 kva or 3.5 kva.
On the 777 if you lose both Eng Gens and the Apu Gen you still have the backup Gen system and then the Rat Gen as well.