Most college campuses already do something similar with safe ride programs. Such programs are usually seen as a good thing, in my experience.

The amount of alcohol needed to be over the legal limit is actually remarkably small and Toronto and other major cities they might possibly do this promotion in aren't exactly known for cheap drinks. Based on that and the high probability that a person who goes out drinking in a major city will not venture too far from their residence, I expect that two drinks would usually be more expensive than a ride home.

Uber fucks up plenty of things that are worth taking issue with, it is my opinion that this is not one of those things. I think most people should see this as a morally positive promotion.