Then I expect I might have a flag for either illegal shift or illegal motion, since the RB is not motionless at the snap.

I think you'll be able to read this from the reaction of the player attempting to call the timeout. If the snap goes off and he's really caught flatfooted, then I might judge this to be unintentional. If he starts moving immediately, I'm shutting it down and flagging it.

We seem to be reading a lot into the intent of the players on plays like this. How do you know the RB did not know they had no timeouts? How do you know the RB did not think the formation was wrong or something else was wrong? As for motion, if the RB is not simulating a start and no other player is moving how is this false start or illegal shift? This very well could be a simple mistake that worked out in Team B's favor.

I see. Although i don't think you can have an illegal motion/shift since the motion seemed legal.

Canadian Ruling
 

Actually, in Canada I believe this would fall under misleading tactics (1-11-2c) and not OC. If you call OC then you would have to allow the result of the play such as a TD to stand since OC is L10 but no cancelling of the play. So it would be L5DR on 1st or 2nd down.

If 14 seasons never had anyone do this.

My bad. In 11 seasons, I do not ever recall seeing a misleading tactic, so I guess I forgot how to admin one.

PS: don't forget the lightbulb! I use it as a visible aid to remind people that it's Cdn rules I talk about.