John come on out to the jobs we work you will see two different raceways coming out of the roof for RTUs.
Unless allowed otherwise.
I was always under the impression the reason the code wanted these conductors separated was to prevent a fault of the class one conductors imposing their voltage on the class 2 or 3 conductors.
As an example I repaired a factory wired display case that had cat 5 point of sale wiring in the same raceway as the 120 power.
The 120 power faulted and put 120 onto the cat 5 wire, this took out the data switch and the cash register.
IMO this is why they will allow you to reclassify class 2 and 3 to class 1 if you then treat the entire control circuit as class 1.
Imaging a 480 fault energizing 18/2 thermostat wire run through the building as class 2 or 3.
IMO the NEC is not concerned with mis-operation caused by induction, that is an inconvenience not a danger.
[This message has been edited by iwire (edited 08-22-2004).]