If by powered armour one is thinking Landmates (Appleseed) or bigger stuff, yes, I would agree, vehicle. If on the other hand it is an armour that only improves certain abilities and perhaps has a power-core for life-support, electromagnetic boots, datapad on the wrist and sensors in helmet etc, then I would consider it armour skill, not vehicle. So it depends on what definition one apply to the Powered Armour terminology.
I might be stupid, but I find no reference in the pdf of Powered Armour, but something along the lines of Landmates would be wicked to have included, I know my players would rejoice! (and so would I).