When I use motion tracking and I have 3 films: 1 filmed from front, 1 filmed from the side and 1 filmed from top. First I track the objects in the first movie and click the solve button, which makes some empties. Can I use the same empties for tracking the next film for more precision? If it doesn't work with empties, how can I achieve this?
Empties are added to the scene as a result of the perspective information obtained during tracking. So no, you cannot use the empties from one solution to track a different camera.
Watch "Track, Match, Blend" to learn how tracking data is gleaned from following features.