Collision not working for mounted T2DSceneObject

I'm having a heck of a time getting collision to work for an object that I have mounted to another object. As far as I can tell, the mounter and mountee are virtually identical except that the object to mount onto the mountee is cloned from a template.

Is there some inherent restriction on collision of mounts, or am I missing something? I've rendered all the collision bounds and they all look fine, and the "spaceship" object collides just fine with "building" objects, but the turret object just passes through. I even set the object type of the turret to be identical to the player's object type and still no collision occurs. Is there something obvious I'm missing?

Needless to say, I'm looking forward to having access to the engine source. :)

Thanks,
Mike

Edit: In case it helps, I've reproduced this issue with a very simple project that I can provide if needed.