Yes you can do. Create a script within FMP that creates a valid FCP XML. You can read the
FinalCutPro XML PDF to learn about how to do.
One major thing you have take care about is the 'updatebehavior' to replace values. With FCP 6 you will probably get updated clips, but the are not in the bins they had been before. With FCP7 they will stay there.
It would take to long to explain everything here.
Hope that's a starting point for you.
Andreas
Spherico
http://www.spherico.com/filmtools