With months of effort researching tripwires and auditing systems, any of them could read your mail.
There's a pretty good chance they'd get caught by some auditing or alerting system they were unaware of though. Many of those systems are kept secret from employees for obvious reasons.
Any two employees collude to much more easily read your mail. There's probably ~1000 people in that position (not only the gmail team, but anyone who writes any kind of library code used by any of the databases, datastores, or application servers). They would leave audit records though, although they might go unnoticed.
A convenient way to put a target on your back. What benefit does this have to their security? Accountability?
I expect that any single Google employee does not have access, in the sense that they've locked themselves out of making changes to their systems without a computer seeing multiple human approvals. But there is a point at which someone can fix that computer.
But yes, my point was that the threat model here isn't "one Google employee goes rogue," it's "multiple Google employees with extremely privileged access to Gmail and/or their code deployment servers all decide that they want to read your email without telling you, and nobody blows any whistles," which seems much more far-fetched.
I thought employees do not have access to user data. Can anyone comment on this?