I don't think you would want to create and maintain multiple automation tracks when the only thing different is the backing track. If you were switching from one version of a backing track to another for every song, you could change Settings > General Settings > Defaults > Recording to change all the backing tracks, and then use the same automation tracks (that also requires that you record the automation tracks by clicking the single recording button to play the default recording, not the multiple recording buttons to play a specific recording).
If you need to change this on a song-by-song basis, you could not make playing the recording a part of your automation track, and instead use the same layout action to start the recording and start the automation track. Then when you want to hear the default recording, you can use the layout action to start it and the automation track, but when you want to hear a different recording, you can select and start the recording and the backing track manually. You would still use the same automation track in either case.