Work with me here....
A1 and B1 both trap the ball against the floor. Each has a hand resting firmly on the ball. Neither can pick it up and neither can gain sole possession. I would call this a jump ball. Both players have control by using the floor rather than their other hand.
I think I would choose a travel call in SupRef's scenario if he lifted his knee while pinning the ball to the floor. In this case, I'd lean toward the idea that he is "holding" the ball there with one hand as opposed to bobbling it at his feet. This would probably happen so fast that you wouldn't have to much time to analyze this too deeply.
And it would never happen...B3 would crash into A1 in an attempt to get the ball and I would probably go with the foul so I wouldn't have to do all that deep thinkin'
