Calculating the "true cost" of nuclear in Ontario is likely to be a damn near impossible task since it has gone through any number of government manipulations and mismanagement as well as some "crafty" accounting to try to hide other expenses.

First, to be clear, a huge amount of the "problems" with nuclear power in Ontario have nothing to do with the technology of nuclear power and everything to do with politics.  The Darlington reactors, which were WAY over budget, is a prime example here.  The bulk of the cost overruns were directly due to government interference and incompetence, not an actual problem with the reactors or their design.

Along the same lines, figuring out something like the "debt retirement charge" has been made virtually impossible.  Ontario Hydro debt was used as a dumping ground for government programs for decades.  Harris split some of it off as "stranded debt", then McGuinty gamed those numbers to no end, none of which was properly disclosed publicly.