Brazilian IRC network that ran a psyced in interserver gateway mode.
Apparently it was the 8th largest IRC network on earth, until they gave in to pressures in form of continous DoS attacks and shut it down.
http://www.brasnet.org/conteudo.php?id=492 used to state they currently have over a million users per day. The existence of such a gateway had been announced to those users and there was a continuous flow of traffic in and out of the gateway.
You could reach a brasnet IRCer by either psyc://brasnet.org/~exampleNickname or xmpp:exampleNickname@brasnet.org
Still, the users weren't so impressed to be able to use Jabber from within an IRC network, after all. They came to talk between themselves, mostly.
<coyo> it's still really cool, though