What you describe in your edit has been happening between the US and UK for decades.
They spy on each other (using the more permissive "foreigner" spying privileges) and then share the data.
I don't see where that says they spy on each other. I only see bits that mention they spy on other countries of common interest e.g. China and share that data.
ECHELON is more relevant for this. (https://en.wikipedia.org/wiki/ECHELON) See especially the controversy section, which shows that the US was using the system for industrial espionage.