The AAIB's initial report states that both engines failed to respond to commands for increased thrust. It doesn't say "the engines failed" or "the engines stopped". In other words the implication is that the engines were still running but were stuck at the settings applied prior to the 'fault(s)' occurring. All the continued talk on hear about blocked fuel filters/ice in the fuel and indeed, no fuel, would surely only be relevant if the engines had completely stopped - something the AAIB report does not state.
Also on the subject of fuel, I have seen/heard it stated several times (including on here) that at that stage of the flight all remaining fuel would have been in the wings and therefore with the fuel in each wing feeding its respective engine. If this is indeed the case, surely the subject of fuel cross feeding is not relevant?