Pit of Shades vs random movement values

[T10]

The core rules describe how random movement values are rolled for to calculate the units Move in that movement phase. 

Are there any official guidelines for how to determine the Move characteristic of such units outside that phase, e.g. when targeted with the Pit of Shades spell? 

I would normally assume the answer is "roll the dice for determining their move for the purpose of resolving the  spell", but considering how literal the devs are with regards to what phase an ability can be applied to it's a risky guess. E.g.: Blood Stalkers don't get to apply their Heartseekers ability if shooting in the Hero phase, because the ability says "in the shooting phase". So maybe squig hoppers and doomwheels count as 0 Move or something and are super-vulnerable to this spell...

 

[Atharen]

I think the technically correct way to do this is to roll the movement of models with random movement each movement phase, regardless of whether they're actually moving, and then apply it until the next movement phase.

I think it's also very reasonable to roll the movement each time it needs to be determined, in this case before resolving the spell.

Importantly, I don't think models with random movement ever count as having a movement characteristic of 0.