I'd be shocked if they came anywhere near email data for Bard training. Why do they need that with all the reputational baggage that comes with it, they have only, like, the rest of the Internet at their disposal?
I can easily imagine people in charge with the mentality of "there's no way that anyone can prove we did it."
It's very improbable, but looking at the "AI integration / product" race it is still a non-zero chance it could have happened.