... Bittorrents already have the ability to encrypt traffic. Once a packet is encrypted then it's impossile to tell what was in it - at least within the boundaries of what is technically practical !
And how's it supposed to work anyway, inspect each packet ? Inspect each traffic flow ? The latter could be circumvented by a slight modification to the Bittorrent protocol to randomise block transmission order !
Then what ? Log and report ? Block ? I for one would be WELL p***ed off to have traffic dropped because it's been falsely classified as infringing. Oh yes, and just because some audio matches a piece of music, that doesn't make it's transmission illegal.