Did you guys ever get this working? Let us know so others (like myself ) can try. Some of us tried getting MUA online going recently, but we weren't successful.
Well, finally we got this to work (me and edward), it only works for danger room online play. (the gameplay quality is lower)
I think it was an IP thing, everyone has hes/shes IP. For example, if I host, I tell you my IP and you edit yours with mine when you join game, and search for me.
On campaign mode, it didn't worked because ... I don't know why.... the team chooser screen blocks.