You don't need a gateway to integrate OCS with CCM. H.323 is a video codec and SIP isn't even a media codec, it's signaling traffic. I have no idea what that reply is relation to.
To allow Enterprise Voice (VoIP) integrate with OCS 2007 and Cisco Call Manager you can either (a) use a media gateway or (b) configure Direct SIP between OCS and CCM without the need for a media gateway. Either way the audio calls will be converted to standard G.711 between environements.
Take a look at this blog article for details on Direct SIP integration:
http://communicationsserverteam.com/archive/2008/09/26/270.aspx