So keeping a listening watch on 121.5 is a requirement and plays a part in PLOC?
Well it's a requirement in our Ops Manual that 121.5 should be guarded whenever practical, and
shall be guarded in areas where interception is a possibility, so there's a few flying around who, yes, are are stuck with that as a requirement.
As far as Europe goes I guess it can now be said that interception has now been demonstrated as being a possibility over (at the very least) Hungary, France and the UK.