In general, there is nothing in the treaty that is going to give Canada or Taiwan any additional rights to tax income. Effectively it allocates those rights between the two jurisdictions. There are no taxing rights in the agreement itself. If there were no obligation taxwise with Taiwan prior to the treaty, this would not create any taxing rights for Taiwan in respect of a Canadian resident.
It does allocate who is able to tax that income and, again, depending on the level of activity being engaged in in Taiwan, it would or would not meet the threshold for a permanent establishment. This ensures there is no double tax. Prior to a treaty, both Canada and Taiwan could have asserted taxing rights. Canada is the residence country; Taiwan is the source country. Then the taxpayer himself is in a situation of double tax to the extent that domestic laws through foreign tax credits do not fully credit the tax paid in a different jurisdiction. This ensures both cannot tax the same income.