The people who pay for a license to use a frequency are the "owners" of that frequency in so much that it is they who determine who may use it. It is quite common at airshows for the tower frequency to be prominently displayed for all to see by the organizers and is taken as an invitation that you may listen if you wish.
Interference with a "protected" service is a totally different matter and is usually dealt with very swiftly by the RA (now part of Offcom.)