12-904 (1) wants to make sure all conductors of a circuit (phases and neutral) are in the same raceway. Parallel feeders can be in bunches and in companion trays. The type and insulation values are important.
As I read it 12-904(2) has the exception that indicates if the cables are:
a)- listed types of armoured cable assembly or
b)- have a barrier of sheet steel
- flame retardant material or
c)- supply and control of remote devices both insulated at the higher voltage.
--the 27.6kv and the 4160kv can cohabitate.
The rule before the exception says "NO" if from different sources. Then the exception(s)
One of the other sections, 36-304 of the Ontario Electrical Safety Code, and presumeably of the CEC deals with installations operating above 750volts "High-Voltage Installations".
Again the rule 36-100(3) states HV cables type TC shall not be installed in the same cable tray as low voltage conductors except if separated by barriers.......with the reference that type TC tray cable installed in cable tray shall be as per Rules 12-2202 and 12-3024.
I note with interest that Rule 36-000 (2) indicates that the supply authority and the inspection department must be consulted before proceeding with such an installation. (Over 750volts) Soooo, You can't get into any financial trouble as long as you do it as per the supply authority and the inspection department under pre-planning for the project.