Actually PLJ started its flip from AOR to CHR just over a month before Z100's launch as a preemptive move. (PD Larry Berger initially denied the shift as a full flip to the trades, but was readily admitting it after after Z100's launch.)
Pursuant to the discussion in this thread, my point was posted with regard to imaging, not playlists. Mr. Berger would likely have encountered a considerable challenge in denying a CHR flip while airing jingles such as "WPLJ Hit Radio 95."