not the op's original question, but I thought I may as well bring it up hear (seems appropriate, and dont want to clutter)
the sob's shield of faith special rule affects sob vehicles too does it not? It was an interesting theory that I thought of a while ago but it never got resolved.
my logic behind it stems from the fact that gw purposefully crewed the tanks with a "sister of battle" and all sisters of battle have the shield of faith. Not only that, but the land raider (I believe, maybe the rhino) can be chosen to be crewed by either a sister OR a stormtrooper or something, lending to the fact that the sister would get the shield.
maybe its an obviously answered question, but I was wondering nonetheless.