To clarify, the example I gave above wasn't at a spawn, it was on one of the hills surrounding the airbase's town. This worked because it was a predictable destination for attackers. But it was kind of like spawn camping, because instead of maneuvering against opponents, I was just sitting there waiting for them, which IMHO is more limiting game play.
MY AH2 counter to people lying in wait to listen and ambush was to maneuver to a higher elevation off the the side, and then in, where I could often see them, and in addition often get flank shots. Since they had their engines off to listen for their victims, I could often get several shots in at very long range before they noticed me, turned engines on, and started to move. With several ambushers, one got even more targets. I haven't generally been able to do this in AH3 due it being much harder to see stuff at long range, perhaps due to the much more dense vegetation, and perhaps due to flatter maps. Elevations needed to be within sighting and gun range of the ambushers for this to work.
MH