So here's the thing...
1- Watch Dogs was mostly developed in Montreal. These are not Ubi Montreal employees - I highly doubt that Ubi would pay to send some devs and PR from Canada to France when they have studios in France.
2- "Console manufacturers tell us what we can keep" is BS, but only sort of BS. It's sort of true in that some devs have to get documents approved and such before you can get an OK to start working on the game. The thing is that this happens super early on, not right before you ship.
3- Parity between console platforms is a given - MS and Sony always want parity, and WILL give you shit (free promo usually) if you achieve certain goals for them. Sony in particular will love you if you also give something to PS+, and exclusive content always means better coverage.
4- 30fps is typically a tradeoff. In life, when you have a job to accomplish, normally it takes 20% effort to reach 80% completion, but 80% work to get the last 20% work done. ~30fps is not always trivial to reach, but is more often than not the best achievable result in a limited timeframe. You have to understand that these devs are always looking for the best possible visual experience from all standpoints, and that to them (and research they've conducted) 60fps does not sell more than 30fps. Great looking screenshots and trailers do, however. If there's a trailer that plays on tv, it ain't gonna be at 60fps, and screenshots obviously don't really care about framerate. Now I prefer 60fps, and I will always prefer 60fps, but it's not as simple as "just work more!" Optimization is a bitch.
So that's about it. They'll always use marketing speak to explain their decisions, even though they are not the real reasons (they'll never tell you it's too much work, except for the mocap thing, which is funny).