Z100's COL is still Newark. They did have their studios in Jersey City until several years ago.
WFAS is a different situation though as it involves physically moving their transmitter out of Westchester and into the Bronx. Even though Z100's COL is Newark, they have always been transmitting from Empire.
That's only kind of true. 100.3 WVNJ-FM transmitted from West Orange, NJ (The WFME site) and WHTZ transmitted at least for a week as I remember from the West Orange site. The move to Empire happened in 1983.