Absolutely.
If the CRTC made such a decision, it would be done through a public process. There would be a call for public comment. It would invite all Canadians to come and give their views on the action it was considering. Then it would take those actions. It would issue an order or a regulation. This regulation or order could be challenged under the provisions that are already in the Broadcasting Act.
One of the first challenges that would come to mind is that the CRTC would have interpreted the act in a way that contradicts freedom of expression. This seems to me to be a particularly remote or unthinkable hypothesis, since, for this to happen, the CRTC would have to have ignored all of these provisions.