During the Second World War, due to heavy bombardment from the Soviets the Allies developed fake buildings which were made to deceive enemies into targeting them to draw attention away from their real counterparts.
Fake Construction Yard could be used to absorb attacks from Soviet MiGs that may have destroyed their real construction yard. These could also be put into outpost bases to make them appear to be full bases.
Fake War Factory was the most common fake building used, because of the high priority the Soviets (and most enemies) have to destroying war factories. With just a few fake war factories up, it would be much more difficult for Soviet MiGs to destroy the real war factory.
Fake Radar Dome could be used as a distraction for Soviet forces trying to knock out Allied radar by destroying their Radar dome.
Fake Naval Yard could be built to deceive an enemy commander into thinking the allies were planning a naval strike, but then the Allies may do a ground strike instead. Even if the Allies were planning to use ships, fake naval yards were built just to force the Soviets to waste time and ammo trying to figure out which was the real Naval Yards.
Additionally, a fake Sub Pen exists in the game files, but is unused in-game.
Fake buildings fell out of use after Stalin's defeat.