Perhaps I should have said you'll always have an AI and an N1. The standby AI was working and I've not seen anything in the AAIB report that suggest the auto-switchover of the engine indications to the lower ECAM display had failed (that said IIRC on an A320 the UNRELIABLE IAS drill requires the pilot to select the thrust to certain physical gates on the thrust quadrant (CLB/MCT/TOGA) so an actual N1/EPR isn't required). Notwithstanding that, the failures in this case were not to do with computers in the cockpit but to do with electrical failure, so is it really pertinent to the thread?
Of course if you are talking about a further failure following dispatch with the lower ECAM display inop then we are starting to get into a whole new realm of possibilities.