The main difference between the 2016/17 bikes and the 2018 ATAS concerning the rear end, the rear mudguard is different, rear rack is totally different, rear footpegs hangers are mounted differently. The OEM Honda panniers fit as they did on the 16/17 bikes. So my guess is aftermarket pannier rails might fit, but I think it’s the relocation of the rear footpegs hangers, that might cause an issue. Best bet is to email the aftermarket pannier company you are interested in, to be sure.
I met a Portuguese guy last week with a new standard 2018 Bike His givi frames from the 2016bikewould notfitbecause ofthe redesign of the rear foot peg hangers. He was waiting for response from Givi. His top late and givi topbox was fine on the new 2018 model (not the Sport)