The link between CTI server and the CallManager is done via JTAPI or it should be IP Trunk (as gatekeeeper to gatekeeper using H.323 or SIP and so on)?
If you are planning to deploy IPCC with Avaya or Nortel, there is no problem to use CT Connect as CTI server. In this case you don?t need Enterprise CTI or CTIOS. I have a deployment with ten Avaya Definity and ICM is used for intelligent routing between the ten Avayas and Envox CT Connect is the CTI Server for the agents.
You can not use CT Connect with IPCC and CallManager, for Call Center purpouses, because CT Connect do?sn't provide Contact Center functions: login, logout, ready, etc. With IPCC and CallManager you can only use CTIOS.
For Avaya, Nortel and other OBXs, Envox CT COnnect provides features to login, logout and change agent states. For CallManager only provides telephone functions, nor agent functions.