The HQ would have to roll as if it moved independently - at least that is how I play it. They can either move with the unit(s) they are stacked with, or move on their own and suffer a possible loss.
Interesting....I could see this as a Home Rule variant. Thanks!
For me, I look at it as the HQ or sHQ cannot move on it's own, per the rules....but that said, I ask, "...why not?" I mean, it's either ground pounders with hardware on their shoulders or tin cans with a leadder(s) in them....why couldn't they move? I'd love to hear the rationale behind that.