i understand that stacking with unburrowing causes a lot of randomized "landing" (when burrowed unit under any unit unburrows, the area that the unburrowed unit finally stops trying to unstack at is the "landing" spot for me)
well....if you create a small area surrounded by cliffs or something normally unwalkable, put burrowed units in there, and some locations on the "cliffs", unburrowing will make the unit go to the location, and since the landing is always random in every time you play the map, it is truly random....
you can use the "bring unit to location" trigger to do stuff.... does this need more explanation or is it widely known already and a waste of time for you and me......?