To answer your question, Ontario is allowed input tax credit denials similar to what Quebec has under its system, but temporarily. It's allowed fully for a period of five years, and then it's ratcheted down. As far as the base goes relative to the GST and the QST, the main differences are that the financial institutions are not the same, although there are smaller differences as well; they have the ITC denials on an ongoing basis, and the QST applies on top of the GST, which isn't part of the GST base.
On December 8th, 2009. See this statement in context.