Walk up to a container, press V when running into it, and you'll clip into or out of containers. I got into quite by accident, I don't remember pressing V to get in, but getting out just press V while running into the walls or the doors.
- Legacy ID
My own Copypasta over from another related post on this issue: (http://feedback.arma3.com/view.php?id=3325)
Camp Rogain appears to be good testing ground for this bug. It contains both cargo containers and the "Military Cargo HQ V1" mentioned, all of which can be vaulted through. Looking down towards the ground and using the Q and E keys to lean left and right while "stepping over" stuff appears to help in pushing through objects.
Also, while facing the wall of the Military Cargo HQ, you can use the "step over" key to push your weapon barrell through the wall and fire off a few shots inside! :P