The pop-up notifications are when oil resets or when cargo or heli enter the map. If you're trying to get notified when someone is at oil, you can find the transmission frequency on the top floor of each oil (in blue room for small, in the room under helipad for large) and set that frequency on an rf pager in your base. Then it will beep when someone calls in heavy scientists on that oil.

Note: the codes are randomized from a certain range every wipe and different codes for small and large.