But I think there's something wrong here:
Even after accounting for the fuel cost hike, most families will come out marginally ahead, officials said.
If most families are coming out marginally ahead, who's coming out behind? And by how much? Is this a Pareto law thing where 20% of the families do 80% of CO2 production and they will all get whacked? And who's paying the government's 25% administration costs on the whole thing?
I suspect it's a median/mean thing, which is sort of like a weaker version of your Pareto law example. You cannot produce less than zero carbon dioxide, so pretty much by definition I'd expect the household carbon dioxide usage to exhibit a right skewed distribution. That would mean that more than half of households would be below average in terms of carbon dioxide production (just like most households have below average income).
For one example of a way carbon production could be really skewed: flying is one of the most CO2 producing activities many people might engage in. In the USA more than half of people won't fly at all in a given year, while 6% of us fly 9 or more times per year. 78% of americans fly less than the average of 2.1 flights per year. So if there was a carbon tax and rebate on airline fuel in the usa, almost 4/5th of americans would come out ahead, even though overall the amount of money being paid in would equal the amount of money being paid out.
The other argument would be if the carbon tax is being applied to a lot of products or goods which are being exported from Canada, then some of tax revenue would come from price increases paid by non-canadians, allowing the program to be a net positive to Canadian households as a whole.
But from the way that quote you found is worded, my guess is it's mostly the first explanation rather than the second.