Just an FYI that I recently discovered using TrackX.
I shot footage on the C100 at 60i. Then, brought the footage into FCPX (most recent version and most recent OS), opened the settings for each clip and selected "de-interlace", which converted it to a pseudo 60p, in order to get a silky smooth slomo.
Unfortunately, when you do this, you can no longer track your footage. So, anytime I need to track I have to leave the footage at 30i.