The tax is based on nationality (non-Canadian citizen) not on "national origin," which is the language of section 15 of the Charter.

"15.(1) Every individual is equal before and under the law and has the right to the equal protection and equal benefit of the law without discrimination and, in particular, without discrimination based on race, national or ethnic origin, colour, religion, sex, age or mental or physical disability."

For example, if the tax applied only to Canadians of Russian origin, it would violate the equality section of the Charter.  However, I can't see how a tax that applies only to non-Canadians would.  They might have more luck with the claim that such a tax isn't within the power of a province.