I've recently been privy to a trick to play Avid MXF files using ffmpeg. Basically it involves forcing (-f switch) the codec (DNxHD). The OP-Atom MXF Avid uses doesn't play without the -f switch, unfortunately. An associate wrote a basic batch file to do this a bit easier, and now we have a basic, rudimentary way to play Avid MXF files - which, previously, was only available within Avid or by paying for the ability.
I was curious anyone else had down something similar, or perhaps can / has ported this over to work under OS X.