I knew something existing on a ruling for this...
$1:
The Green Party raised the challenge after its exclusion from the 1988 debate, arguing that CBC, CTV and Global violated the Television Broadcasting Act by not providing equal time to each political party. The Ontario court ruled that the debates were not partisan events, which meant equal time rules didn’t apply. “While participants in a debate may very well be partisan, the program itself, because it presented more than one view, was not,” the Canadian Radio-television Telecommunications Commission wrote in its notice explaining the decision.
The Supreme Court of Canada refused to hear the case.
...but.
$1:
...at least one local channel in Ontario is volunteering to take the place of the major networks. Channel Zero on Wednesday said it would invite all leaders - including Ms. May - to a debate in its Hamilton studios that would be made available to other stations as requested.