We have been searching for a solution to play out to XDCAM using firewire or USB, while editing in Media100 suite. The best way is to export the Programm as self contained or by reference and import it in Final Cut Pro. If exporting to XML some effects might not transfer.
But there is a Bug: While exporting by ref or as self-contained, the clip will not be given a reel name, as it does when exporting to XML. This reel name is needed for the export to XDCAM feature in FCP (export to XML does not need it!!) otherwise you will get an XML Parse error. You can add any reel name manualy in the browser and you will now be able to export to XDCAM using the export function in FCP.