Unmerging 'merged' tracks?

Have been handed 40 hours of spectacularly recorded (4-8 tracks) steam engine (train) sound FX. Meaning each clip was recorded with up to 8 mics (it varies). Whoever set up the project 'merged' each set of 4-8 tracks to a single 2 track 'merged' clip in FCP. So I have all these 'merged' 2 track clips which, if I 'link' them, split into usable stereo.

I want to cut the soundtrack for the film in FCP (using the stereo 'merged' clips), then send the project to STP to do the mix. BUT! When I get to STP I want to be able to 'unmerge' the stereo clips and work with the full 4-8 tracks.

Any hints or tips would be most appreciated...

Ben