APR would not have caused this accident IMO. It simply boosts the fuel schedule...ie it adds some fuel to what is already manually selected. If you are at flight idle, APR would simply increase RPM a little bit...it would not cause th engine to go to full power.

If BOTH engines were at full power, there is only one common point between the two engines that I can think of: The throttle cables (they are cables on the 100/200). A structural failure along the path of the cables might have pinched them and jammed them so they could not be moved. Or they might have been cut or broken, which would leave the engines in whatever power setting they were selected at when the cables failed.

Also, you don't need the throttles to shut the engines down, the respective Fire Switchlight will do it for each engine. If the throttles cables AND the fire system failed...well they would be very lucky to get on the ground in one piece, cuz there must have been some serious problem with that airplane.