Ticketing will be in the North Terminal (South Terminal is all-Delta). I'm not sure where their ticket counter will be at (I haven't been in the main terminal building in almost 3 weeks), last time I was in the North Terminal, they were putting some finishing touches on Frontier's new ticket counter (maybe JetBlue will be at Frontier's old counter). They'll most likely be on D (The ATL
website doesn't list it yet, in fact it needs to be updated because it still lists Corporate Airlines as going out of D (not T) and the site doesn't yield any info), and JetBlue's site doesn't give any gate info either. They'll more than likely use one of the gates on the South end of D (my guess is D-5 or D-7).
As for Baggage Claim, I'm guessing #3 in the North.