Yes we have, we have installed a PA system with background and MOH, also loaded into the ip office403 MOH file that also plays.
You can plug virtually any CD player into the audio port on the rear of the system, programme the CD player to play repeatedly and this will cover you (check the output volume on any handset by entering *34).
Also if you paste into the manager file a music file called HoldMusic.wav, when you reboot the system it will automatically load this file into the systems memory (The file has to be at a certain sample rate, which at this moment I can not remember).
I hope this helps.