Depends on which building burns down- Notre Dame was saved essentially by its massive stone construction- I think most of Toronto's major buildings will likely be much more heavily damaged due to their less permanent construction- for instance, with St. James, the entire roof and everything inside the church would likely would be lost. It might even end up being a Christchurch situation where the remnants can't be stabilized and the remaining walls will be torn down.
Regardless, buildings like St. James, St. Michael, City Hall, or Queens Park would likely be rebuilt in some form- but likely not in the same way, as Toronto doesn't have the same deep cultural connection to those buildings the way Paris has.
That leaves the reconstruction up to more interpretation- architects will be salivating at the opportunity to put their own 'spin' on the reconstruction, whereas with Paris, there will likely be a heavier citizen push to restore the spire as it once was (though I expect the Macron government to still push for a modern interpretation).
I sort of dread the results of this competition:
https://www.dezeen.com/2019/04/17/notre-dame-spire-competion-news/ and what reinterpretive proposal will win, like what a few cheeky Brits are already proposing:
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The new spire on Notre Dame could be a “super-slender needle touching heaven’s clouds”, a minaret or a work of art composed entirely of light, according to some of Britain’s leading architects.An
www.thetimes.co.uk