Russian
If my Russian is not rusted entirely, it works like this:
If we have XMQP switched on, and another player also have this switched on, and his commander has "6th sense" trained, we see grey bulb by his marker. When he is spotted, the bulb turns yellow. There can be other situations, like vehicle in fire, vehicle overturned, or vehicle drowning indicated by other icons taking place of this bulb.