That article seems very dubious. Germany had 400 active agents in Iran, in late 1943? Tthe country had been under Allied occupation for over two years. Plus German intelligence had been thoroughly compromised by Double-Cross.
Stanley Lovell, OSS chief of R&D, recounted a similar story in his 1963 memoir Of Spies & Stratagems. It supposedly involved an OSS agent code named "C-12", who was deployed among the natives of the Kurdish mountains. A group of men arrived by parachute in the area: a German assassin team. "C-12" got himself hired as native guide, and led them to Tehran. There they rented a house and planted explosives in a tunnel under the street used by Churchill and Roosevelt to go to the Soviet Embassy for meetings with Stalin. Then he stole the detonators and reported them. Lovell had no official report of this story, and he wrote that "C-12" later denied that it ever happened.
There was a 1943(?) movie with a similar plot but I can't find the title.