Yeah, had the same thing with a solo AV breezing along 500 feet below a flight of three of us for a good 3-4 minutes. Roughly same course (I think his waypoint was the same airfield as ours), none of the AI pilots showed the slightest interest. Alvin was happy. I was neutral, since I'm not fond of the limited movement range of the gun on the BE - used to pointing and shooting with my single-seat campaigns, though I've been very successful with Strutters in a 70 Sqdn campaign.
I think a lot of it has to do with the two-seater AI (see the same thing in RoF) - if they've got two seats, defense seems to be in their blood. If an enemy aircraft comes into the gunners field of fire and range, the gunner will usually open up. Pilots will generally continue on blissfully until the plane starts getting hit, and then they start evading, but to escape the fire, not to attack.
It's irritating, but at least with your kills you'll probably get promoted soon, and be leading your own flights much of the time.