haven't tested spikers, but they are afraid of detached plasma turrets and ghosts when there is a rider in it. (human or otherwise)
I've managed to get a brute to chase me in there but he uh... died (of natural causes I swear) before the engineers could grant him shields. If he has the shielding when he is killed do they explode as if they were attached to his squad?
Oh, and as far as I noticed, they didn't really freak out when the brute was screaming and chasing me...
I watched the video and took a some pics of me screwing around and some other stuff (Including the brute at squidhenge). I'll put them up later though.