Added models of cars were deleted for various reasons. For instance the burnt cop car was used for a scene of a mission. Someone even found the jet from the last mission of TBOGT that lets you walk in it. Scenes in GTA IV and EFLC are all Made with real object from the game itself. By using this technique the scenes were more realistic but people found some of the objects, or damaged models of cars... Every GTA has extra or deleted cars.