i dont wanna be that guy, but the match up just doesn't work.
of course the code of the mafia says to not deal drugs. theres a lot of rules that get broken, but we never really see tony dealing drugs.
we know uncle junior and richie were dealing coke on the garbage routes, and tony put a stop to that.
the different between walt working with gus and working with tony is that tony is under relatively constant surveillance. the fbi KNOWS he is a criminal. they just can't technically prove it. or at least prove it to a degree they want to.
so its almost impossible to make the logic work to where tony would be messing with walt, if we are trying to keep both characters in their respective worlds with their respective "rules" in tact.
as far as mcnulty and lester being able to catch tony, i dont know about all that. like i said before, the fbi is pretty much on tony and his main crew a good amount of the time. they have phones tapped, bugs planted, rats wearing wires.
we're obviously talking about a very prolonged investigation on the part of the fbi. basically unlimited money and manpower.
if jimmy and lester had those things at their disposal, maybe they could do it, but no way to tell.