Sure they can, the Soviet Union interred damaged B-29's that diverted to Russia. Uncle Joe, our ally, didn't bother returning the US property. Instead he ordered the B-29 to be reverse-engineered. Their exact copy was the Tu-4 'Bull.' China may still be flying some of their copies. Later, more advanced Tupolev bombers were built with design features from the Superfortress. Look at the tail turret of the Antonov An-12 cargo plane and you're looking at the tail turret of a B-29. Boeing definitely needed to sue the Russians for patent violations.