Note - there is a fair degree of supposition in the following, but it may be worth considering.
If the engine oversped to the point of the power turbine wheel bursting (but not the compressor turbine), with this engine there would be no indication of an engine failure, and hence no access to the contingency power ratings.
This has happened before - the power turbine wheel disintegrated, and the compressor ran up to maximum fuel flow in an attempt to get the N2 signal back to 100%. Needless to say, since the compressor was working just fine, there was no engine failure declared by the computers, and the 2 minute and 30 second power ratings would not automatically be avaiable.
In the earlier incident, the pilot had time to look inside and figure out something was wrong and selected the correct engine to shut down. This allowed the contingency power ratings to be used and he landed safely. But the cockpit indications would be very confusing -on 'bad' engine- N1 and TOT maximum, zero torque, zero N2. 'Good' engine would have N1 and TOT appropriate to torque and good N2 signal. Probably have both low rotor warning and overtorque warning on at the same time. (Could you figure this out if it happened to you??)
Like I said, quite a bit of supposition here, but it may help someone who is trying to sort this out.