I've learnt that police impounds allow you to get back your vehicles that disappeared after cutscenes, as well as vehicles inside which you were when you got busted. I've also heard that they can be used as save garages(like the safehouse garages) and they often exhibit strange behaviors(cars spawn on top of each other, partially inside each other, partially submerged in the floor etc.; also, planes and helicopters have been know to spawn inside police impounds, especially the one in Roca Escalante, Las Venturas ).
However, impound garages don't function this way for me. They very rarely behave in a strange way and they don't spawn my vehicles that disappeared after cutscenes, nor do vehicles inside which I was arrested appear in the impounds.
Can anyone explain?
IMPORTANT NOTE: I play San Andreas(and all my other games) on PC. I've never used consoles and I know almost nothing about them. Maybe the impound garages behave in the way described above only on PS2.