Some of this might sound uncharacteristically mind from "moi" - who has apparently donned the virtual "King of No HD" sable cape - but I really doubt iBiquity and the Alliance had a goal in mind of deliberately interfering with independent broadcasters. First of all, if you were to collectively dose the management at perpetually-arrogant Big Group Radio sodium pentathol and ask what they think of their smaller competitors, they'd spit PATOOEY and dismiss them as non-factors (witness the typical BGR attitude of Guy Wire for one, plus other posters here.) So there's no upside there for them. Secondly, the worst victims of adjacent-channel hissing are...their OWN stations (witness WRVA versus the three 1130s in the midwest, CBS unholy trinity of pink-noise 1010, 1020 and 1030, WWVA vs. WHAM etc.) The situation has been aptly described here and elsewhere as "Mutually assured destruction" (the ghost of Tony Marvin will forgive us the reference.)
Citadel didn't say they wouldn't repair their HD crap, but they HAVE made their analysis of HD-AM clear, and it certainly isn't favorable. It's ludicrous to argue that a hybrid system which can only operate digitally in daytime hours has any future. That's just stupid. It doesn't help any AM broadcaster to be a "digital daytimer," even if the hybrid system worked acceptably when it IS on, which it doesn't. Cox simply turned their HD-AMs off, oddly keeping their iBiquity gear installed but not operating (likely because of legal advice about contractual commitments.)
Back to smaller market stations - the hope that the little guys would move to EXB couldn't have been an Alliance objective for the simple reason the FCC isn't accepting any new-station apps for EXB. Nor is there any prospect they will any time in the forseeable future.
No, it was just arrogance, non-engineering savvy management being bamboozled by a connected, powerful few, short-sightedness and stupid greed (the hope that HD's developers would recoup their investment at the expense of non-Alliance broadcasters - a gentler way of saying, "picking your competitors' pockets.") Now that it's spiraling into the most notorious bomb in radio-industry history (think New Coke and Edsel with transmitter sites) the focus is clearly shifting to the blame-laying and face-saving mode.
The desperately touted digital FM power hike will be entertaining to watch. Pop some popcorn and pull up a comfy chair.