"Other European countries also work closely with the NSA, he said, describing the organization as "in bed together with the Germans." Other countries don't ask where the NSA's data comes from, and the US returns that favor, to give politicians plausible deniability in the event of source disclosure, he explained."
We knew this 25 years ago when it was revealed that the Canadians (under Echelon) spied on cabinet ministers who were thought to be disloyal to Margaret Thatcher. This avoided the potential legal issues of using British intelligence services to spy on members of their own government.
German cooperation with US spying is made fairly obvious by the numerous Echelon stations dotted around Germany.