I'm not sure I follow you. However, one method of passing data between voice systems is via DTMF.
Say you send a call out from UCCX to an Avaya system, and want to send it an account number. You could perform the Call Consult Transfer, and outpulse the DTMF of the account number. The Avaya side would have to be expecting the DTMF in order to process it.