Hi Christopher,
I have not done this, but it certainly is supported on CME. The details are noted below;
Configuring Music on Hold from a Live Feed
To configure music on hold from a live feed, perform the following steps.
Prerequisites
•SIP phones require Cisco Unified CME 4.1 or a later version.
•VIC2-2FXO, VIC2-4FXO, EM-HDA-3FXS/4FXO, EM-HDA-6FXO, or EM2-HDA-4FXO
•For a live feed from VoIP, VAD must be disabled.
Restrictions
•A foreign exchange station (FXS) port cannot be used for a live feed.
SUMMARY STEPS
1. enable
2. configure terminal
3. voice-port port
4. input gain decibels
5. auto-cut-through (E&M only)
6. operation 4-wire (E&M only)
7. signal immediate (E&M only)
8. signal loop-start live-feed (FXO only)
9. no shutdown
10. exit
11. dial peer voice tag pots
12. destination-pattern string
13. port port
14. exit
15. ephone-dn dn-tag
16. number number
17. moh [out-call outcall-number] [ip ip-address port port-number [route ip-address-list]]
18. exit
19. ephone phone-tag
20. multicast-moh
21. end
From this good CME doc (with detailed steps);
http://www.cisco.com/en/US/docs/voice_ip_comm/cucme/admin/configuration/guide/cmemoh.html#wp1010511
Hope this helps!
Rob
