I couldn't find a topic relating to this so here goes. The Ont.electrical does not mention insulating existing walls that have knob and tube wiring. Would this be covered under the building code? I know it's not a good practice but who actually regulates this. Thanks in advance.

You would not find anything in the building code regarding blown in insulation in a cavity where knob and tube exists. But if you wanted to make a case where you wanted to point out it could not be done, that would be an electrical code issue. In this case since knob and tube wiring gives no temperature ratings, you could say it is not then suitable to be enclosed in thermal insulation since it is not marked as such. However I know there are hundreds of homes out there that would have insulated attics with knob and tube, not saying it is right.

2-124 of the 1986 Canadian electrical code does not prohibit thermal insulation . It states that the insulation must not put any stress on the wire associated with the weight of insulation. Insulation with a mettalic face must be kept 25mm away from K&T.
Loose blown in insulation is OK with any type of wiring method recognized by the code.