I have AVCHD footage from a Canon XA10, which was shot in standard interlaced 50i mode.
When using Log & Transfer to import it, it is encoded to ProRes 422 as 25p (field dominance is set to none in the clip properties). This is visibly wrong.
I tried both FCP 6 and FCP 7. Even though I had more import options in FCP7, I found no way to specify I wanted interlaced ProRes in the Log&Trans import.
In FCP settings, I have selected 50i, Top field first everywhere I could (though it only appears to matter in the sequence settings).
When taking the clip into the 50i sequence, I am prompted to convert the sequence. I have to say "no" for the images to play correctly. But playing just the clip in the viewer, it shows terrible interlacing artefacts.
I have exactly the same problem, same camera, using FCP 6. The L&T process turns the 50i clips into 25fps clips with No Field Dominance.
I have tried all possible variations of forcing the clips to take on different Field Dominances (Lower, Upper) and matching these with a variety of sequence settings but although I can make the programme look great in the canvas, as soon as I export to QuickTime the picture has horrible interlacing problems.
I have found another references to this problem but no fixes.