There is no comparison between even an old first gen Motorola P25 radio like an XTS3000 with current HOST/DSP and these lousy excuses for digital scanners when it comes to performance on LSM systems.
I suspect your state radio might have either an old template (prehaps before Atlanta migrated to their current P25 system in 2009?) or the ID is no longer valid. You might want to contact the DOAS help desk, might be time for a codeplug update. You will probably get the new UASI "value combo meal" template which will give you most of the basic stuff in Atlanta.
I STRONGLY DISCOURAGE any attempts at programming an agency owned radio. Doing so is actually a violation of the Georgia Trespass act, OCGA 16-9-93. I am sure you already knew that, but some reading this may not.
It is possible to program a radio up for passive monitoring of these systems using a personally owned radio privately obtained. It also requires advanced programming, not to mention the software and cables. All of this is covered elsewhere on other sites but it is not for the novice and don't expect someone to jump help do it for you. Not trying to sound harsh, but it is the way it is.
FWIW, Cobb county has it up their butts they MUST replace our current phase 1 system with phase 2. The new Fulton county DTRS will also be phase 2 capable, though initially most county talkgroups will be phase 1, only the "roamers" from the soon to be Unified Radio System (North Fulton) will be TDMA.
I have heard encryption will be used heavily on both systems but we shall see. The new Fulton system is supposed to be live by July 1st. Not sure about the URS.
Too bad the new scanners everyone is excited about seem to be more of the same old, same old discriminator tap based crap. APX anyone?