Well, it could honestly just be the virtual inventory of a hemmt. You would have to kill the cops and everyone around and then lockpick the vehicle. This would force you to either bring your own vehicle or just take the vehicle with all the loot inside. Another interesting thing they could do, like some high-interest convoys in real life, have decoys as well. either having multiple "loot" vehicles in the same convoy but with 1 true loot or having them split off and having the civs and rebels gamble for the right one. The 2nd option will have the routes planned out for the civs to know, of course