I know this is a necro-post for a 2 or 3 month old post, but I still wanna chime in.
Last I heard, there were no plans to include voice chat in BO2 because it was deemed "not worth it", which to me sounds like "the coding and technical issues are too difficult for us to deal with."
I hope in the future that we actually get true voice chat in Black Ops 2, because one of the defining characteristics of old Xbox 360-era multiplayer games was the rabid trash talk and angry gun game knife reactions. I played Search and Destroy a lot back in the day on Xbox 360 mainly FOR the interesting and funny interactions I had, because EVERYONE used voice chat in that specific mode.