I'm not at all familiar with CUCM and MOH, but CMR Premises is hosted on your on-premises TelePresence Server. So in order to get MOH into the TPS lobby, it would have to be built into the TPS, or somehow brought in through CUCM if at all possible.
If you cannot find a solution, suggest you contact your Cisco Account Manager, and see if they can suggest a solution and if not, have them open a feature request to have it added.