This is hard to answer, as there are multiple ways of attacking a shot, so i’d probably need to see the actual footage.
If you can show me, you can send it to martinb [AT] imagineersystems {DOT} com and we’ll take a look.
Briefly, if you only require the transform motion, then you may be okay, however if you are requiring a corner pin, then tracking another plane will not work to get the correct data for another plane. We have ways of dealing with this in mocha Pro via the Insert tool or Camera Solve, but not in mocha AE.
But we’re happy to take a look at the shot itself to see if there is another approach.