(b) to the extent of their application to criminal investigations or prosecutions and except for the purposes of Parts II and III of this Act, the Convention on Mutual Administrative Assistance in Tax Matters, concluded at Strasbourg on January 25, 1988, as amended from time to time by a protocol or other international instrument, as ratified by Canada, or a comprehensive tax information exchange agreement that has effect and to which Canada is a party or a tax treaty, as defined in subsection 248(1) of the Income Tax Act; (accord)