I'm on the experimental build of BATC and it currently get's GSX to start pushback when I ask BATC for push back and engine start, and on arrival when I request gate BATC gets GSX to assign the gate and marshaller if necesary. It does have some hiccups but that can be down to incorrect gate numbering in scenery.
Mostly it works really well and you still have the option to open GSX and select it yourself.
