The contact object is only exposed by enumerating the ChatWnd.Contacts property or the Messenger.MyContacts property.
js code:
function OnEvent_ChatWndCreated(oChatWnd) {
    for (var oContact = new Enumerator(oChatWnd.Contacts); !oContact.atEnd(); oContact.moveNext()) {
        Debug.Trace(oContact.item().Email+' : '+oContact.item().Blocked);
    }
}
/*
    for (var oContact = new Enumerator(Messenger.MyContacts); !oContact.atEnd(); oContact.moveNext()) {
        Debug.Trace(oContact.item().Email+' : '+oContact.item().Blocked);
    }
*/