Forgive me if this seems disrespectful, but shouldn't teams that are interested and capable of playing Xball carry the burden of contacting the body that organizes it? If it is associated with the Millenium, contact the Millenium board. If it is seperate, it needs to announce it's existence in whatever way it sees fit.
Joining a league has always been the job of the team. The League, if there is one, should announce its existence and terms and then await responses.
Gilt invitations just drive up entry/ franchise fees. Maybe by invitation only is reasonable, but it isn't the only way or the traditional way.