Highspeed,
I am typing this from memory (and I my memory has not been very good lately
), the 777 manual volume 2 as I remember it cleary stated that the 2 IDG and APU are the main AC power systems.
It has no mention of the BUG being a main AC power system.
So as they say, "in the subsequent court of enquiry" you will be grilled, toasted, deep-fried to charcoal bits by this little smart-ass lawyer trap.