When I send jobs off to my sound designer for work, I give him AIFF files of my primary audio and a quicktime movie of the timeline.
He works in ProTools and Logic with both of these to score our shows and features.
If there's a way to XML the project over to Logic, I'm not aware of it as it's never been asked for, but I would start with the Logic Manual which would be available in the "Help" menu of that program. Simply search for XML and that would take you to the answer.
You could also try searching for "Logic" in the FCP Help menu.
Walter Biscardi, Jr.
Editor, Colorist, Director, Writer, Consultant, Author. HD Post and Production Biscardi Creative Media