The C++ monitors N2 input signals to the DECU and not NR speed, so the likely hood again of both engines showing a overspeed (real or false) again very unlikely.
The common link is the collective lever postion anticipator that will sense increase or decrease in collective position to adjust power settings.
I noticed in Sasless comments the Torque went to zero , in CYCCOLL report only stated a significant reduction in torque.
I also am very interested to see what happened to this C++, I have many of them on the base I work at.