You do realize that Microsoft is also willing to cooperate with Sony, right? That doesn't quite mean anything. I can understand your other points but this one doesn't quite fly
Do you mean crossplay? I don't really look at that as working with Sony it's mostly a thing that (right now at least) would benefit MS the most as it'd give them access to the tens of millions of ps4 users playing games as well as the ones on PC too. With Nintendo I was referring to them making a ds viva pinata game or saying how cool it'd be to have Banjo in Smash. They'd never work with Sony on an actual game, one that could theoretically help Sony move consoles or strengthen their online presence.