I can't claim any special knowledge of Beatrix beyond the information that was circulating about her when she was still a candidate, and not the Divine. But based on that... I think if she'd negotiated at all, it would have been in good faith, if with a playing field tilted heavily in the Chantry's direction. Any agreement that was reached would have been honored.

But I'm not certain that the negotiations would have happened in the first place. If they did, it would have been because she decided cooperative mages were important enough to the fight against Corypheus that the risk of losing them was intolerable. That's a high bar, though it was more or less the one those of us who were striking were relying on in the situation as it played out. I expect her calcuation would have depended how the war was going at the precise moment the Inquisition resisted the pre-strike requests that it allow mages a say in what happened to their own phylacteries.