I don't think it was Butch.First of all,there wouldn't be any pressure from his captains because Butch turned his back on Phil.Phil's #3 was there,so was Little Carmine and the guy who set up the meet,George Paglieri.
The captains probably agreed with his decision because otherwise Butch himself would have been killed.

And if Butch was to whack Tony,that would restart the war,seeing as how they didn't have their own Jersey guy anymore(Burt Gervasi).
If that was his intetion all along(make himself boss and wipe out Jersey),why not kill Paulie Gualtieri too?They had that meeting(the one Carlo missed)...