Below is a video made by BatmanArkhamVideos that shows all of the assault locations. Using the locations from the video I created a map that shows each of the 16 assault locations via an orange dot.
After visiting all the locations, if some assaults did not appear (All will not appear in one fly though the city) then enter then exit a building to refresh the map.
It is also suggested that when you are looking for assault to fly around in detective mode. In my experience it seemed to make the assaults more likely to appear.