Very interesting move here in Philly.
When CBS and Westinghouse merged, Westinghouse had to sell rock powerhouse WMMR-FM to avoid FCC monopoly charges. Looks like they're jumping through hoops this time to avoid having that happen again.
Re the WIP move: I'm guessing that the FM station will get to keep the call letters... which is a shame, since it's only had the call letters for three years, while the AM station has been an important part of the city's history since 1922. (Did you know actress Anne Hathaway's grandfather was WIP's "Morning Mayor" in the fifties and sixties? Well, now you do.)
Back in the seventies, WIP, which was then a music station owned by Metromedia, ran the CBS Radio Mystery Theater weeknights at 11, but changed the name to "WIP Mystery Theater" so that people wouldn't think they were the CBS station in town. My, how times have changed.
-Tim