You don't see it much anymore, because you don't see umpires throw all that much period (though the guy in the 1st Boston game did). Anyway - it didn't use to be rare for a catcher to toss a ball out of play and the ump throw a new ball out (instead of handing it to the catcher) without the live ball every going dead because of a play event - it's dead by virtue of the catcher having tossed it. I suppose in theory there is an explicit TO there, but it's all so automatic that it's never sensed.