Thanks all for the replies, I shall investigate further!
edit:I can confirm h-'s observations about the vehicle explosion.
However, this simple test case shows no info sharing between groups:
- 1 friendly unit (player)
- enemy group A (with no ammo) can clearly see me (knowsAbout 4)
- enemy group B cannot see me, and is about 100 meters from group A
Group B's knowsAbout of the player remains at 0 indefinitely, even if I fire upon group A, assuming group B do not detect the play on their own.
It seems the sharing behaviour is dependant on really loud actions (eg, satchel, destroying a vehicle)