What you can do is, mount the defaultPackage network drive into your windows explorer.
http://localhost:8080/drools-guvnor/org.drools.guvnor.Guvnor/webdav
This is where the process definition bpmn2 files go.
From there, this discussion might help you:
http://community.jboss.org/message/621173#621173
I did not have the time to do a complete manual roundtrip. If you manage to get through with it, it would be nice if you could share it here.
I hope this helps.
Cheers,
Tobi