[mbyron]

BU makes his call as if nothing had happened. Remember, the offense has the right to take the result of the play, so it's important to get all calls right. Who knows: maybe after that out at 2B F4 throws one away, after BR had touched 1B, and BR ends up at 3B. In some situations, the offense might take R3 w/ 1 out over R1, R2 w/ 0 out. The ball is live after catcher's OBS, and it matters what happens during that time.

In the OP, if I'm BU I have heard my partner say "that's obstruction!", so I call the out at 2B and wait to see if the defense will turn a double play. At the end of playing action, I call "time!" (if PU hasn't) and let PU make the award: BR to 1B, R1 forced to advance to 2B.

In my experience, I sometimes have to explain to R1 (now R2) and/or F6 why he's not out, but that's not an official mechanic.