Boston doesn't need syndication for weekday evenings, period. Would WZLX put Alice Cooper or Nikki Sixx on weekday evenings? No way.
I've read in several places that 102.5 WKLB does skew its playlist to make it more "Northeast friendly," putting more emphasis on country music from more mass-appeal artists and ones that are more likely to cross over to mainstream. Artists and songs that are a bit more "twangy" and get airplay on more rural/Southern markets are not likely to get played on 'KLB, especially if the song stays below the top 20 on the country chart. IIRC, Big and Rich's "Save a Horse, Ride a Cowboy" took a while to get played on 'KLB, although WCTK/New Bedford-Providence had it pretty early.
An observation -- as I work on the South Shore, it seems that, from the businesses I go into, the people I speak to, bumper stickers, etc., that WCTK seems to be the preferred country station over WKLB. This is in the Hanson/Hanover/Bridgewater area, where both signals seem to be about equal. I find this kind of interesting.
Jacko