Redsy:
A multi-wire circuit is a 3-wire edison, the nice thing about it is if you balance the loads the neutral carries no current.
The picture is the same one I saw yesterday at HD on a heat/vent/light unit a 3 switch deal, I posted the about that discovery but it never showed up.
The Nu-tone i saw friday at my supplier recomended a seperate 20 amp ccircuit. This is in addition to the mandated 20 amp circcuit for the bathroom. This is how i do it too. As i implied before I believe that two cables is in violation, even if I didnt Our inspectors insist that we use flex or MC Depending on how many switches are involved.
Three (3) switches we can use 12-4 MC cable and 4 switches flex, greenfield. I usually make up 2 or 3 ahead of time cut to different lengths just to have them on hand.