I guess the eleventh commandment applies!
which makes me ask...
and with the jet we never got to fly the long STAR that we always got with the PA46. I asked about the reason and the answer was that if you had PRNAV the controller was able to give you a different route,
how did ATC know you have PRNAV approval in the jet?
In theory there is a database of PRNAV approved aircraft, which in theory is accessible to ATC, which in theory could be done in real time.
If you look at e.g. Zurich, which last time I looked was totally closed to all non PRNAV IFR traffic, how does this work? It's obvious that ATC there don't operate the system anyway.
Airlines also are faced with HUGE bills
Why don't the airlines get together and tell Eurocontrol to get stuffed? I went to a Eurocontrol "navigation workshop" a few years ago (a complete farce, basically) in which they claimed that they are under huge pressure from the airlines to reduce the route charges, so they wanted to dismantle the radar network and replace it with ADS-B. Notwithstanding the absurdity of this "solution" it did appear they are concerned about what airlines tell them... or so it looked.