The Hipath 4000 UV2.0 software does not support SIP, it's H323 only, and I doubt very much that connection will be supported to the Avaya switch.
In my opinion, you would be better making a QSIG connection from the Hipath 4000 (DIU-N2 card required) to the Cisco, I'm sure Avaya could do the same, and let the Cisco equipment take care of the IP.
With a multi-vendor installation on old unsupported software, that will be the most trouble free path to take.