There's not much info as to exactly how this stuff works, other than what USA Today has reported:
CNN will have 44 cameras and 20 computers in each remote location to capture 360-degree imaging data of the person being interviewed. Images are processed and projected by computers and cameras in New York. There'll also be plasma TVs in Chicago and Phoenix that will let the people being interviewed see Blitzer and other CNN correspondents. Bohrman says the network can project two different views from each city so Blitzer can appear to be in the studio with two holograms.
Jessica Yellin was the first CNN reporter to be "beamed" to the New York newsroom, where Wolf Blitzer interviewed her -- and she reported that there were only 35 cameras pointed at her, and that "talk to the cameras in New York." Apparently representatives in the Obama campaign in Chicago and the McCain campaign in Phoenix will be interviewed as holograms later in the evening.
It's still unclear who makes this hologram technology, nor how much it costs, nor how exactly it works.