My pro tools guy is working fine in 24fps. We cut 24fps (not 23.98) and I gave him 24fps QT movies (with TCB) that play out to his NTSC monitor in ProTools just fine. I am sure the same would work with 23.98.
If he NEEDs 29.97 you could make a new sequence thats 29.97 and copy and paste the entire edit into that. But that just seems like it would be more headache trying to synch back into your 23.98 sequence after he is done his work.