landan's request had me wondering...
For other people's information, there is a feature on the MEGA share page to be able to search an entire share for specific tracks.
In the case of my share, I had two hits on the phrase 'Cinnamon Belter', on ZPBX and ZPCP. At that point it would be easy to select the track(s) and download them.
Just suggesting it might be an easy way to find out if tracks are already being shared...