Google Analytics cookies are first-party cookies, so are tied to the domain of the website you're on, not Google.

Google Analytics data, unless manipulated to be otherwise by the end user with a manual customization, is not systematically tied to personalized Google+ traffic information. There's never been any evidence otherwise, and honestly, the burden of proof is typically on the accuser when making these kinds of accusations, so, really, I flip the question to you and ask what evidence do you have for this accusation besides insinuation and conspiratorial instinct?