If the local franchise granter (Gwinett County government) signed off...then it is OK. The local cities (except for Roswell and Atlanta...and maybe a couple of others) don't have PEG channels...so unless carriage of the Gwinett PEGs was a condition...then they don't.
If Gwinett County didn't...they can do various things...including taking the matter to court. It depends on the language of the franchise agreement (which is public record and subject to the Open Records Act).
Comcast tried to move PEG channels to all-digital in Michigan (assigning channel numbers in the 990s). A big stink ensued, with local government threatening fines. I think the matter ended up before a judge, but I am not sure.
Check the 990's to see if there are two new channels. This must have been done when History and TV Guide were given the boot to digital.
Contact the Cable TV Franchise Authority in Gwinett and ask them about it. Also, check the last couple of bills to see if there is anything on them about it.
Comcast will end analog service next year in Atlanta...exact date not set.
In Cobb...23 and 24 are still on analog and digital simulcast last time I checked. Comcast really wants to get rid of analog to make way for heavily compressed digital.