Cisco SRST multicast MOH does not support unicast MOH.
Only a single Cisco CallManager audio source can be used throughout the network. However, the audio files on each SRST gateway's flash memory can be different.
Cisco SRST multicast MOH supports G.711 only.
Multicast MOH support for H.323 is unavailable in all versions of Cisco CallManager 3.3.2. For more information, see CSCdz00697 using Bug Toolkit.
In the Cisco IOS Release 12.2(15)ZJ image for Cisco 1700 series gateways, Cisco SRST multicast MOH does not include support for H.323 mode.
http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a00802d1c31.html