blizzrd
Micromanager
If there's an approaching unit in the 4x4 box (actually x-1 to x+2 and y-1 to y+2 (i.e. it helps to approach from the east and south)) then the functions for flipping the city and units become active.
Do you actually mean that it helps to approach from the east and north?

It would surely have to be a box from x-1 to x+2 and y-2 to y+1 for it to help by approaching from the east and south.