There are 3rd party software out there which can do a much better job at broadcasting wave file, send live page, text notification, weather alerts, etc.
If you want to develop yourself, you need to use RTPTx, RTPRx and CiscoIPPhoneExecute objects from SDK. To broadcast audio to a multicast, there is also sample code available. The problem is managing the phone list and groups and providing an intuitive interface for users and sys admins. I do have some sample code that we used in PhoneTop Messenger product, but it is all in Java and needs a Windows box to host it.