From Justin Farmer of WSB:

After speaking with some City of Atlanta politicians who wish to remain anonymous, many remain skeptical that the "private funds arranged by Cobb County" will hold up and that this deal with "either turn out to be publicly funded by the residents of Cobb County or that it will completely fall through and the Braves will awkwardly remain at Turner Field."

While admitting this is all speculation on his part, one official put it this way "you don't just raise half a billion dollars in private investment without anyone hearing about it." It could turn out this has all been a game of brinksmanship by the Braves and City of Atlanta. It's difficult to say at this point what's going on.