I'm not a minister of finance, but I can understand that in business, positioning may be strategic. You may decide to print things in the United States because they have to be remailed and it is easier to do it from there, and so on. I understood the mechanics behind it, I don't need any proof other than what you are giving.
In any event, if Canada Post is doing the job, and I think that corporation does an exceptional job in Canada, it can even go and try to get market shares, starting when it is deregulated.