Report in The Wall Street Journal for edition published Jan. 6 2022 (and on WSJ website presently) indicates that DOT and FAA negotiated a deal with the two wireless carriers based on a "term sheet" reportedly reviewed by WSJ. Would be interesting reading, most likely.
U.S. DOT and FAA have (per the article) agreed not to seek or demand further delays. In addition to the current two-week delay, the federal authorities accepted the limitations most recently proposed by ATT and Verizon.
Without seeing the "term sheet" (and having any technical information in it explained properly), it is a guess to say that some plans appear to have been outlined, at least, for engineering, testing or other technical steps toward validating lack of interference or extent of any potential interference that does exist or might exist.
The major passenger and cargo airline trade group, Airlines for America, reportedly has elected to hold short of filing in federal court (presumably motion papers for a TRO, Temporary Restraining Order - though it's an easy call that this thread has already overstayed any welcome that might have existed for lawyer-speak, let alone more details about that fascinating federal procedure topic, "How to Stay an Agency Order When a Reconsideration Petition Still Is Pending").