Not sure it's Zucker behing the scale back at CNNI. When AT&T look at it they probably think why are we doing this. So anything that is salvaged will be good. However moving things to Atlanta makes little sense as CNN Center can't have any long term future.
A little bit of both probably at play. I don't think it's a coincidence that AT&T takes over, Tony Maddox retires, and then the ax swings the week after.
As far as consolidating everything to New York, that was a plan rumored years ago, and while a lot has moved up there, I can't help but think that CNN will never leave Atlanta altogether. Especially if the entire company is very cost sensitive right now, then Atlanta is a good, cheap place to conduct business. They already have a ton of established infrastructure and resources there, and worker compensation is lower than in New York. Most of CNNI, digital, and a lot of other core departments have never left Atlanta even if all of the weekday Domestic live programming left.