CBS has lots of alternative ways to play the chess pieces, especially if they can convince the FCC to consider WLNY as part of a separate Long Island ADI (not a hard thing to do if they either consider primary coverage contours as they now exist, or slightly directionalize WLNY to take a little notch out of the western part of their signal pattern and remove any remaining doubt).
Read the column, Bob...

There's no such thing as an "ADI" anymore, and Long Island is very much part of the New York Nielsen DMA.
But what CBS is doing is using the FCC radio/TV cross-ownership rules, which have nothing at all to do with DMAs. Those rules, unlike anything else in the FCC's ownership limits, look specifically at stations' cities of license and signal contours. The "markets" that exist under those rules are determined by which signals completely cover which other stations' COLs.
So in this case, we have only two COLs to consider: CBS Radio's six existing radio stations and WCBS-TV are all licensed to New York City, of course. So is 101.9.
When considering whether 101.9 fits under the cap, the CBS argument (supported, I think by the rules) is that you must consider two "markets." One of those is defined by the New York City limits, and includes any station with a signal contour that completely covers the NYC limits. There are enough of those stations to create enough independent "voices" to allow any single owner to hold six radio and two TV stations, or seven radio stations and one TV station. What CBS is arguing is that within that "market," CBS will have only seven radio stations (six existing plus 101.9) and one TV station (WCBS-TV), and that WLNY
does not count because its signal does not cover all of New York City. The sleight-of-hand here, if any, is that the rules were created by looking at analog signals, and have not been rewritten for DTV. In the absence of new DTV rules, CBS is using the "noise-limited DTV contour" to determine WLNY's reach; we'll see if the FCC buys that argument.
(The other "market" is defined by the Riverhead corporate limits, and that's far enough from NYC that none of the New York-licensed stations put an attributable signal over Riverhead; that market therefore consists only of WLNY as far as CBS is concerned.)
These weird COL-based rules have affected CBS before. When CBS bought KOVR(TV) in the Sacramento-Stockton market, it had to study both the coverage over Sacramento, where it already owned KMAX-TV, and Stockton, the COL for KOVR. It turned out that one of CBS Radio's San Francisco stations, KFRC 610, covered all of Stockton...and that was enough to put CBS over the ownership limits for the KOVR "market" unless 610 was divested, which it was.