The integration is only available in the US right now, and only for about 50 cities (Boston, Chicago, New York City and San Francisco are some of the larger examples). It won't work everywhere that Uber and Transit are available, unfortunately.

With that said, there's no doubt that Uber wants to see this feature expand. If it's going to create a viable alternative to owning a car, that means acknowledging that riders can't (or just won't) always use its service for the entire length of a trip. You might be more likely to use Uber if you see it as part of a larger transportation picture, especially for those times when it would be cheaper to take a shorter Uber ride and bus the rest of the way.