I would imagine that the investments you are referring to—lost income, as you put it—likely come from sources outside the country, for the most part. The banks have subsidiaries in the islands of Jersey, Guernsey and so on. That money is derived from activities that are not Canadian, activities that take place outside Canada.
So, if Canada were to change the law to create a tax with what I mentioned, income that was not generated through a business activity would be taxable here in Canada. But when you have a bank operating in Africa and making profits in Africa, should those profits be subject to Canadian taxes? I think not, but that could change.
It is up to you to decide and to make recommendations.