Unfortunately, after reading all the comments it would seem nobody here is getting the reason. The view is all singular. Strictly from a programming and jock point of view, absolutely it's the worst idea for that stick. There would have been so many better format choices and revenue opportunities. Now with that being said, from a corporate radio business stand point in the PPM world, this is a brilliant move on CBS radio part!
In the PPM world TSL is not a factor and total gross impressions are the driving force behind the numbers. In a market like Sacramento, numbers tend to stagnate and even more so in PPM. By creating another format for the station or becoming a single competitor to another station, you'll only see marginal shifts in numbers. Mostly in the two competing stations. KNCI and KNTY are perfect examples of this. However, by doing what CBS has done and with a sizable marketing blitz you stir the entire pot, and change overall listening patterns with the CHR, AC and classic hit formats. Plus, with the change KZZO will undoubtedly see sampling go up which effects overall PPM numbers. A station like KSFM may see some shifts in audience number, but the format is isolated for the most part, since most people in the market consider it a hip-hop station and not close enough to a mainstream CHR or AC to cause any real degeneration of it numbers. So CBS was not worrying about cannibalizing itself in that regard.
With this move I would expect some new excitement in the market, strictly from a new CHR battle one that hasn't occurred since the KSFM, KWOD and KROY days. Granted It won't be like that again, but I still suspect that over the next month or so you'll see is some new positioning from all involved in the battle to retain audience share and even a little capitol being spent to defend against the competition. These kind of battles are good for the audience and over the long term can, if done right, be good for the radio market as well. This will cause some movement in PPM and as things heat up, could create a couple of jobs for some local talent in Sac. It's too soon to tell, but ultimately this was a wise move on CBS radio's part.