Agree with the idea that getting rid of differential noise is best done with an isolation transformer rather than relying on AC cable twists.
One interesting article I read a long time ago suggested that a significant benefit of armored cable in general, including bare-armored-ground (BAG), was that lightning surges were carried better by the armor than the ground conductor inside due to actual skin-effect issues with high frequency strikes. The armor seems to have performed as a very low inductance path. Can't say I noticed a big improvement in noise when I used it though.