It depends if the jaws of the pocket are still considered the 'playing surface', kind of like the top parts of the rail with cloth.
If this happened with the CB, I believe, though am not 100% sure, that the CB has to be lifted straight up and if the OB falls into the pocket, it is re-spotted. If it does not drop, it stays where it comes to rest, providing it doesnt interfere with another ball. On either occasion, it would be a foul. But, like I said, I'm not sure of it. I just think I remember seeing it written that way.
With 2 OBs, Unless there is an actual rule, it would just be more sensible to consider them both pocketed and resume shooting, unless you can come to an agreement where one is pocketed and the other spotted.
I was referring to a one-pocket game. Games such as 9-ball or 10-ball, the ball would stay pocketed and not spotted.