The tiles had already been lifted and fenced, so Tony knew the deal was over and done with. I guess he figured he may as well get his beak wet. But as to what's up with Silvio, I honestly don't know. It seemed he was miffed at Patsy's getting passed over as acting capo for Christopher: "It's the way certain people wanted it," he said at the meeting, like it wasn't what he wanted...plus he was an icicle to Chris afterward. But why he did such a foolish thing with Patsy ("I got your back"), I don't know, unless it was a little revenge thing against Tony. When you watch it again, TIS, note Silvio's cold, dead expression as Tony talks to him about it in Tony's basement. It's like he's so apathetic. I wondered, too, if Silvio "got wired" after his arrest in season 3. Wouldn't that be a kick in the head?!?