I would not say that anything is impossible, but it really is not possible to do what you describe. The file is what it is from the time you shoot it and does not change. Of course you could move the camera alignment during the event but most people align their camera with cues (short ticks of tape) that appear as streaks on the film. If the ticks are there in one shot but not in another, the camera has moved. This not probable as once a camera is aligned, it is usually left alone until it is taken down after the race. Any assumption that a timing technician would try to manipulate results is highly unlikely. I for one have no stake in who wins or looses, only for providing an accurate record of the athletes achievements.