The following report posted by Kevin Darling to newsgroup rec.aviation.military, February 27, 2003*:
I've seen at least two USAAF magazines that mentioned these captured planes. Here's one article from June 1944 "Air Force", the official service journal:
"THAT B-17 AGAIN"
"A Nazi-manned B-17 cropped up again recently to give some of our bomber personnel a few anxious moments. The bomber, captured and reconditioned by the Germans after being forced down over enemy territory, tried to get "friendly" with some of its American cousins when the latter were returning from a raid on Brunswick.
"The tail gunner of a bomber in the No. 3 place, high position in the combat wing, saw a B-17 approaching from six o'clock out of an overcast, slightly below the formation.
"Our planes went into a cloud and became separated, and the gunners on the bomber from which the strange B-17 was sighted lost track of other planes in the formation. They did see, however, flashes but not tracers, from the top turret and left waist guns of the straggler. It fired for several seconds with its guns pointed at our planes.
"As the enemy B-17 came out of the cloud, it stopped firing and came up on the AAF plane about 600 yards below. The tail gunner could see no lettering of any kind on the tail fin. One faded star without a circle was seen on the left wing, and the entire plane was painted a faded brown. The tail gunner warned the ball turret man about the plane. The strange B-17 fired again from its top turret at the U.S. Fortress, and our ball turret gunner returned the fire, observing several strikes on the enemy. The strange B-17 went on underneath and disappeared in a haze. It inflicted no damage."
Note: In "The Possum and the Eagle", the author also mentions running across a German flown B-17.
* MID 8e4ac002.0302271335.6f536b3c@posting.google.com
More on captured B-17s/"Do 200"s and a photo
More, including histories of some individual captured B-17/"Do 200"s