The thing about ETOPS is its statistics.
If one engine fails on a twin jet the statistical chance of a second engine failing on that aeroplane during the 180mins 240mins or whatever, are so remote as to be an acceptable risk.
You cannot use ETOPS to justify single engine public transport.
As for reliability, I have never had a core engine failure on a turboprop. I only know of one that happened in my previous company (20+ twin and 4 engined tps) was when the turbine exited the rear of the engine at FL180.
However. I have shut turbo prop engines down for - gear box failure, generator break up, auxiliary drive failure, high oil pressure due oil cooler flap failure, electrical prop control failure etc etc.
Again the reliability of the core engine is not in doubt. The accessories are another matter.
Another point about changing the rules in Europe. The caravan etc MAY have a sufficient MTBF now, but if you change the rules these aircraft will still be flying in 40 years by which time they will be so worn out that the loss rate would grow to unacceptable levels.