So I will ask for speculation again. If Airbus seems so certain that this was not a manufactures fault, then as most seem to agree here, it must be a maintenance issue, what error on the part of maintenance would cause such a sudden catastrophic failure?
We assume since there was no PAN or Mayday call that this took the crew completely by surprise. So no loss of oil, no chips, no vibrations or strange sounds. I can't imagine what single error ( missing bolt, nut, TQ value ,etc) could account for this, especially since this was not a new MGB replacement, so something done during regular running maintenance.