[Reference] Extensions of the Hive Mind

If your army is Battle-forged, all Troops units in Tyranids Detachments gain this ability. Such a unit that is within range of an objective marker (as specified in the mission) controls the objective marker even if there are more enemy models within range of that objective marker. If an enemy unit within range of the same objective marker has a similar ability, then the objective marker is controlled by the player who has the most models within range of it as normal.