You can mention Uber, but there are many more companies. There's Lyft, and Facedrive, and all sorts of new companies that are coming on the market.
Some may be located in Canada, and some are not. For those that are not located in Canada, normally the way the system works is that if a driver receives a service from a foreign company of that nature, which is an intangible service, they would have to self-assess the tax and claim input tax credit, if they're allowed to do it.
By being registered, the taxi business would receive a service from the foreign company of providing a match from the driver to the passenger. This amendment doesn't force a foreign company to collect tax. It's legally very difficult to force a foreign company to collect tax, because you have no enforcement mechanism on them. They're not located in Canada.