Currently everything uses the default Cisco MoH stream. It was relatively easy to create the new audio sources for MoH, but what took me a while was figuring out how to apply that new source to the queues. Most information I Googled mentioned setting them in the CTI Points... It was only after figuring out that that didn't work that I came across an article that correctly stated you had to change the CTI *PORTS* not Points. Our UCCX server was using a single Call Control Group with 100 CTI Ports for both the sales and support queues, I created a second Call Control Group and moved 50 of them to the new group. Then came the fun part, going through all 50 CTI Ports and setting the MoH source.
So in a nutshell, if you want to use different MoH audio sources for the queues on your UCCX (or IPCC) server, first make sure your CRS scripts uses the standard Call Hold and Call Unhold commands. Then create a Call Control Group for each queue and create or shuffle around your CTI Ports so that you have enough in each control group, and finally in CUCM locate the CTI Ports (they are listed under Phones) change the MoH source for each port.
Hope that helps.
-Keith