I have had to export from FCP to AE on PC working from a DV50 timeline. I just exported as self-contained Quicktime and imported into AE. Specific to the project, I was exporting as an animation self contained QT file (so I could preserve the alpha channel/transparency info). Worked great for my needs.
If you are talking "roundtrip" workflow like Motion/soundtrack pro - I don't know if that is integrated with AE as I've never done it.
