Although the PABX does not support Video Codex, it may be possible to work around this by doing the following:
1. Phones and PBX must be on the same subnet
2. Both extensions must have the reinvites enabled
3. Both extensions must have replaces header disabled
4. You must have the devices not bound to the media server
with this setup you might be able to have 2 devices supporting video codex to communicate between themselves