Very, very rarely do I recall noticing the same, where factions that are supposed to be allies appear to be firing on one another.

As a player, when accidentally causing too much damage to a friendly or neutral NPC, that unit and all their friends will turn hostile toward you, until you leave the area.

Does anyone know if this perhaps works in the same way for NPC's? If an NPC unit happens to accidentally down the shields of another unit in an allied faction, would they turn hostile towards one another in the same way, for the duration of that encounter? Would this even happen between units in the same faction?