Frankly I read about all this years ago so I'd have to spend a lot of time looking all this up and that's unlikely at the moment.

I may very well have some details wrong.

Re: parallel construction reference here though clearly this is more recent: https://techcrunch.com/2019/03/28/hemisphere-phone-records/

At the bottom of this article it references the NSA and Snowden but says no explicit links was proven. https://en.m.wikipedia.org/wiki/Parallel_construction