В книге правил всё подробно описано, откуда вот подобные вопросы возникают у человека, играющего в ваху многие годы, ума не приложу.
BATTLEMENTS AND BUILDING DAMAGE
A unit on the battlements is slightly less prone to harm if the building suffers damage. They're already on the roof, so that roof can't fall in on them, however, there is still the possibility of injury from shrapnel and so on. Accordingly, if the battlements are damaged, any unit on the battlements suffers the same number of hits as a unit inside a building would, but these are resolved at Strength 3, not Strength 6.
ABANDON THE BATTLEMENTS!
If a unit Falls Back while on a battlement, or the building belov' suffers a total collapse result, there's no time for those on the
battlements to make a dignified escape - they must jump for it' Resolve this exactly as described for Leaping Down (see above)