I don't think the mayor won this strike. And I know the people of Toronto, particularly the children who went without pools and summer programs, the students who went without jobs, and anyone within smelling distance of an "emergency" garbage dump lost. So quite a few commentators argue that the union won, that the city "caved". In the short term, that may very well hold true. But in the long term, the unions signed onto deal that prolongs the problems with the sick bank by postponing a resolution. In effect, union negotiators, and the members who ratified the deal, have kicked a problem down the road to their successors.
The city negotiators who first accepted a contract with the sick day bank provisions might have hoped the city would prosper enough to fund the eventual payouts with no difficulty. Unfortunately, the union should have no illusions about the problems that the compromise they have accepted will create. Whether future contracts come up for renewal in good times or bad, in every future contract the union will have to face the option of giving up the sick bank for all employees in return for a larger pay increase, or perhaps even a smaller pay cut. In other words, until the union finally accepts the end of the sick day bank, members will face the same choice at each successive contract: fight to keep the benefit for some of the workers, or trade it for something for all the workers.
Allowing a contract clause that keeps a perk for some workers but not others flies in the face of what unions represent; it creates a permanent division and conflict of interest in the workplace. That would cause enough trouble, but for the next few contracts, the greatest conflict will take place between new workers and those hired in the 1970s and early 80s. Given the demographics of Toronto, this means a conflict between a young and very multi-cultural cohort entering the work force, possibly with an actual majority of workers of colour, and a more "white" cohort nearing retirement. Unless the poisonous legacy of two centuries of modern racism evaporates over the course of this contract, CUPE has bought a serious challenge to solidarity over the next two years.
I don't call that much of a win for the union.