From memory there were discussion here on the Logic forum where the general opinion was "it doesn't work". Thank you for your findings, I will try it out next time I need to do some video syncing.
For what it's worth, the Ripple Training people explained more than a year ago how to do audio post in Logic from FCP X (they have a YouTube channel, you may search there for more info). I do remember they also stressed the importance of assigning roles to the audio tracks but I don't recall the steps to actually export the audio files into Logic.
Thanks again!