Vanilla Arma 2.14 (no modifications)
Example on Stratis Airport:
1) Place the first MK21 Centurion AA Turret on the end of Airport, + a UAV Operator as Player
2) Place the second MK21 Centurion AA Turret on the other end of Airport BUT empty and put a OPFOR Soldier into it
3) Place some big Rocks or some big Houses like Tanoa Office Building between both MK21 Centurions, and you will see the enemy turret in your Radar
4) Optional you can turn the Turrets in oponent directions in 3DEN and just look what the Turrets do, they will turn the turret and target to each other and dont mind the Rocks or Buildings between them.
Also noticed if you test it directly as SP Spectator they do not react to each other, if you go from Spectator Mode to Player they will react.