I have questioned the Class 1 thing a few times and it is possible. You just need to follow all of the class 1 rules from end to end.
The chance of coupling harmful amounts of 60hz in any raceway that is not measured in miles is infinitesimal.
You are generally talking about 2 balanced conductors for each voltage. The twist necessary at 60hz is what you see on transmission lines.
If the raceway is actually a "duct" (referenced but undefined in the NEC) cable jackets can be the isolation although they usually have an additional isolating innerduct/raceway in there.
BTW along these lines, I have also heard the argument that a cable jacket is "isolation" so if you had a chapter 3 and a 725 cable in the same raceway, they are isolated. You just can't terminate them in the same box (generally).
The scenario was you have a raceway with a (say Romex) in it. You have "T" body conduit body at each end just before you enter the chapter 3 box. You come in the side with a low voltage cable and exit before you get to the box on the other end. Is that legal?
It is a conversation starter anyway.
