The US system is great
and I really mean that. The taxpayer and airline traveller pays for it all, even for us foreigners
Or the FBO picks up the tab from the profit he makes
Skidkid
I am not sure you have dealt with the depths of semantics in our industry to any great extent, reading your post. Yes, ICAO makes it 'mandatory' for 123.450 to be designated an interpilot frequency outside VHF ground station coverage. No, it doesn't make it 'mandatory' for it not to be used anywhere else in VHF ground station coverage areas. Hence it is used by facilities in such locations, eg Danish sector oilrigs, authorised by the appropriate CAA.
That's keeping it relatively simple of course. ICAO 'rules' are only ever standards, guidance and/or recommendations, they have no legal force. That is for each State to legislate, or file a difference against. Many, including the UK, do.