American intellegence agencys are prohibited by charter from spying on American civilians. Same with British and Australian agencys.
So they cut a deal. Each uses it's full power to spy on the others civilians and does'nt interfear with the others spying on their civilians. They then report back any 'interesting' information to their partners overseas. A pissing contest was held when the English used infomation gleaned from their ops to help Airbus win a contract but mostly it's been smooth sailing.
very interesting