In my experience i could tell you that the OmniPCX it´s an open plataform, an you should not have any troubles interconecting teh 4400 with another systems, thas as long the others systems will be compilant with the international standards (H323, SIP, Q.SIG).
I´ve had Known that in Peru Alcatel and Argentina Alcatel have some cases of studies on solution with CISCO.
If you have another question, feel good to send it to me, I´ll be gald to tried to help you.
Luis Fernando Martínez
DIMA – ALCATEL