Unfortunately we only have tested the Intercom feature with Axon and cannot give support for its use with other PBXs (the Intercom feature does not follow an open standard and therefore is not intended to work with other products).
Having said that, are you sure your port 8000 is not blocked? If you run an Ethereal trace on your PC where you get no audio, does it pick up the RTP packets ? if not, that means they aren't getting there, somewhere along the line they are being blocked.
