They don't get the benefit of the doubt. I've lost count of how many times these agencies have been caught illegally spying only to apologize and keep doing it in secret. There's probably even a Wikipedia page of all the whistleblowers.
Even if they don’t have free reign over every bit of data (unlikely), there are certainly automated systems that will give them free access to any account they wish upon delivery of a rubber stamped “warrant”, signed by an anonymous “judge” in a secret court.
https://www.zdnet.com/article/google-the-nsa-and-the-need-fo...