If the a/c was enroute YYZ/LIS and it's only got as far as the Azores that seems like an awful lot of fuel to suddenly 'lose'.
I don't know the 'bus but an uncommanded fuel dump, if it could happen would not empty a tank, surely it would only reduce to a stack pipe level.
What with the GE90 compressor failures last week ETOPS could be going the same way as the dinosours
