I don't personally use XDoclet, but may other do. Michael is working on adding some new JBossCMP tags and documentation, but that is all I realy know. If you don't get a good response here, I suggest you post to the jboss-users list.

I had a similar problem and went digging in the XDoclet source. There is a template in xdoclet\ejb called jbosscmp-jdbc_xml.j that specifies what XDoclet does for the undocumented @jboss:relation-table tag. I wasn't sure if it was necessary on both sides, so I just took the hack and slash approach and put it on both. I put code like the following on both sides of my many to many relationship:

/**
* @return Returns the production staffers (TPSs) assigned to this content development project.
*
* @ejb:interface-method view-type="local"
*
* @ejb:relation name="content-development-project-tps"
* role-name="one-content-development-project-has-many-tpss"
* cascade-delete="no"
* @jboss:relation
* fk-column="TPS_Id_FK"
* related-pk-field="id"
*
* @jboss:relation-table table-name="ContentDevelopmentProjectTPSLink"
* create-table="true"
* remove-table="true"
*/
public abstract Collection getTPSs();