If you place the proxy mines on the red marked spot (screenshot 1), you have a chance to get it in the middle of the container. When it is in this spot, there is only 2 ways to retrieve the mine back.
Only ways to retrieve this back:
- Place 2 new mines.
- Have an airstrike from an enemy Skyhammer destroy it.
P.S. The mine does not explode if somebody is next to the container.
http://puu.sh/jdEzS/3f1df281e2.jpg