I'm using the popular 'Dynamic Universal War System' mission, version 0.75, available on Steam Workshop and also discussed here: http://forums.bistudio.com/showthread.php?160117-SP-Dynamic-Universal-War-System-%28DUWS-alpha0-1%29
This is a mission that creates various enemy hotspots around Altis; in my particular configuration, 16.
In this scenario, the enemy won't engage me, and my team won't engage them. This apparently happens from starting a mission. Bizarrely if I use a helicopter (e.g. the Pawnee) to shoot at them, sometimes they return fire.
The author of this map puts the blame for this at BI's door. There is also a reference to a fogging issue, already on the tracker: http://feedback.arma3.com/view.php?id=14232 - however in this later instance of the mission, fog is apparently disabled, and indeed none is visible.