I'm not entirely sure that's the case, and even if it's what the letter of the agreement says, there's no reason the two parties couldn't revisit the arrangement.
But there's also no real reason to move the WBBM-FM calls to 105.9 this late in the game, is there?
For every practical purpose, 105.9 already *is* "WBBM" to anyone who's listening. Nobody but us cares about the quick bit of "wcfsandwcfshd1elmwoodpark" that blows by right before the top of the hour.
Nor, this late in the game, is there any real reason to return the WBMX calls to Boston. While there's some anecdotal evidence that national ad buyers didn't immediately understand that "WWBX" was the same station they'd been buying as "WBMX," by now you'd have the same issue switching Boston back.
My best guess? 104.3 becomes WSCR-FM because there's no good reason not to change the calls to match the format, just as Audacy has done over the years at KMOX-FM, WINS-FM, KNX-FM, etc.
If they think it's worth keeping the WBMX calls away from competitors, it's probably more likely they get parked out of market on some random AM than that they risk disrupting national sales by swapping out calls on 96.3 or 105.9.
And I still maintain that in 2026, we don't need callsigns at all and it's probably time for them to be deregulated out of existence.