idealy you want 2 trackers, one for you and one for the police.

JFB tech, although you are right that containers are a good blocker, they dont totally block the vhf signal tracker uses so if you have a decent 3 way GPS/GSM/VHF live tracker then it will show a live trail to the container then if response is quick enough, a vhf signal that can be picked up within a mile as opposed to the 5 miles or so for a cop car tracking a car on the road. Aircraft can track much further ranges.

Thats why you want your own tracker so you can live follow the car before the container is shifted. Trust me, if you ring the cops saying ive found my stolen car and will retake it by force and assault people, they will come dead quick to protect the criminals from being assaulted