Place a static .50 or grenade launcher and a group of enemy AI infantry, both sides facing each other.
Make the AI infantry approach the static and they will shoot the gunner without getting fired upon. (even placing alot of static weapons so they have plenty of time to return fire doesn't solve it).

Tested this only on longer view distance settings so far. (2km or more).

EDIT:

After testing some more I believe this issue should be expanded to all AI inside a vehicle as well. Although the static weapon AI is the most obvious problem as they should have the normal infantry spotting ability in addition to their visual aids for spotting.

Other vehicle-based AI has the same problem. While the situational awareness in most vehicles would probably be dimished by numerous factors, they should have very good spotting abilities in the direction their optics are pointing. At this moment the technical aids for vehicle based AI seem to be ignored and only their reduced situational awareness is accounted for. The overal result means that infantry is to powerful against vehicles (and statics) at longer ranges.