The CT7 has an overspeed sensor in the power turbine, to protect it against a loss of load (shaft breakage, etc.) However, if the prop were to fail to fine pitch at a high IAS, it could probably drive up to the overspeed trip even with the core engine (gas generator) shut down. In that case the o/s trip is of no help.
However - as I mentioned before - I see that as very unlikely with a counterweight prop such as Dowty. The counterweights will always attempt to drive the blade toward coarse pitch.