Is the CTGateway SIP compatible? Can it be used to route traffic between Non-Mitel SIP devices? My question is in regards to video conferencing equipment.

The CT Gateway is not a SIP application. Inter-Tel created CT Gateway to tie the OAI data streams from multiple Axxess systems into one. Inter-Tel did have a SIP Server application that you could use to connect SIP standard devices to the Axxess IPRC cards.