However are Bombardier, and in the background the QC Province, bargaining smartly enough? Of course if there is no business incentive for AB, then it can drive the reportedly imminent deal to their own optimal terms - I wouldn't dispute that.
But allow a reference to the prior deal. Press reports indicated that AB was becoming obligated to bring its worldwide marketing, sales and support, and presence to bear in favor of the A220 program. Has AB done that sufficiently, and in accord with and fulfillment of the deal's terms (assuming the contract and related documents from the original deal, in the hands of a competently assertive attorney, provide a realisitic basis for "pushing back" on AB)? From QC's perspective, one could realistically expect that no stone will go unturned in endeavoring to keep jobs in aerospace here. AB has plenty of finance capacity, or so its apparently unblinking response to a four billion dollar civil penalty would suggest. And QC, and more broadly Canada (and its friends) could have pretty long memories. Not least the intensity of loyalty to the French-speaking tradition is easy to underestimate - but the sting when resentment is applied is not easily forgotten.
I don't know what the deal documents from the first AB deal say, but I do know that the entire earlier deal occurred in the grips of a strange, totally uncalled-for Tariff Delusional Fever from someplace south of Mirabel and Dorval, and it stands to reason there is leverage to be found from that earlier, hasty or hasty-seeming deal, if wise business people only will look for it. (Notice, no possible wisdom is claimed for any lawyers, SLF here included.)