Microsoft has been doing XMPP for the last 6 months or so with facebook via an xmpp service running at 'beta.xmpp.messenger.live.com' and it looks like its now public, You can use psi and other xmpp clients to connect but it requires X_MESSENGER_OAUTH2 sasl authentication.
Manually specify the host as beta.xmpp.messenger.live.com and connect using <username>@messenger.live.com
