Well I have the Beta version available to me in the Play Store and I had auto updates turned off, because I didn't want the update.
I wasn't getting the newest beta version in my update outside of the Play Store, but just the newest public version. When it would update, it would still show I needed an update in the Play Store.
Also the other night when they had to switch out my phone and I was updating via WiFi to Lollipop, I got notice it updated.
I had not logged into this phone with any account, so the Play Store was not available to me. I saw this on my notification screen.
Also notice, that is not a Play Store notification with that big fat Facebook icon.
Also this isn't the first time Facebook has done this, they did it two years ago.