[App_rpt-users] How to replace Allison with custom prerecorded messages?

We're running private emergency system outside of US, nodes are permanently connected to each other so theres almost no need to play any messages. The only messages we need is "Connection to server is lost" and "Connection to server restored" played by node, and sometimes we need to playback emergency message that uploaded to our system's HUB. How to remove/replace Allison with custom prerecorded messages? Thanks/