Dixie, they can only wire the lawyers office if they know that they can prove that criminal acts are being conspired within the place. I saw this mentioned in the Stanfa book, but basically they would've had to have had a previous wiretap somewhere else which proved to them that Cavaliere's law office was being used in that manner, only then can they wire the place up. That's if it's like our lawyer/client privilege law here in the states.
You are certainly right about Leonardo/Stefano's possible involvement in the plot to murder Desjardins. I've only really learned that Boucher was supposed to be persona non grata with the Hell's. So if that's true, which I don't really know now since the reportings of his involvement with Wooley. But if it's true, he would've needed some extra muscle, the Rizzuto clan could've supplied that. They're involvement is clearly possible and I wouldn't doubt it at all.
And I think I've heard those tapes. Are one of them of Vito talking to some guy about his car being stolen and him telling the guy he got the car back in another call?