I got my ATP with my initial in a CJ. My examiner pretty much kept to the flash cards given to me by FSI. and asked a few basic and I mean basic aircraft question. Pvt and comm pilot oral questions. At the time I was working for a 91K operation, he said he would ask me a few far questions, opened up the FAR/AIM laughed and then closed it and said, "you good". In my experience, as a student and CFI, your ATP is purely a rt of passage. Not some 8 hour CFI initial oral. Have fun. You know the aircraft. You should be fine.