the basic run of the mill field ack isn't hardened that I have noticed, what seems to be harder now is actually hitting it. If you score a solid hit it still only takes a couple pings with .50's to silence a field ack battery but actually getting a direct hit has gotten much harder.
I don't believe the ack has been "hardened" in the CT, but I honestly haven't tried to strafe it yet either, if for some reason it is set above normal I'll check and see about fixing it tonight.