Yes, and an intern would be subject to a code review before pushing to master - no way would they have write access to the "master" repo.
https://www.facebook.com/publications/514128035341603/
And I assume they have extra requirements for interns to push code.
I liked this idea too : "all engineers who contributed code must be available online during the push. The release system verifies this by contacting them automatically using a system of IRC bots; if an engineer is unavailable (at least for daily pushes), his or her commit will be reverted."
That way, they are be able to react very quickly in case of a problem.
I doubt that an intern on Google would've access to the search codebase. I'd wager that only a handful of trusted employees have access to that codebase.
On a small company, I agree. But on FB they're around 5k people. Let's say they have 3k engineers, that's a awful lot of people they're trusting with their source code