I may be TOTALLY wrong here, but doesn't PRS apply to publicly aired recordings (jukeboxes, telephone hold music, elevator music, radio broadcasts)?
If a pub covers band plays a song, there is nobody there to keep notes of what was played, they may not even know who wrote it, and if the "promoter" (in this case presumably the pub landlord) had to pay for every song that a band played, it would be the end of live music because they couldn't afford it.
I realise that Queen are on an arena tour, but the principle is the same and if it can't work at one end of the spectrum, it can't work at the other either.
Having said all that, if subsequently a live album is released, royalties accrue from SALES of the performance, but not the original performance.
Let the shooting down of PG commence....