Can I install Symantec AntiVirus Enterprise Edition on CallManager Server 4.2(3) ???
I would not recommend installing the full Enterprise Edition suite as it will not be TAC supported.
It looks like from Symantec's website that Antivirus Corporate Edition is one component of Antivirus Enterprise Edition. See the following link. It's possible that the Enterprise Edition would allow you to install only the Antivirus Corporate Edition component. I believe this would be acceptable.
Hope this helps.