It's difficult, and I can tell you that since writing my paper I've had some talks with some of the provinces that are interested in what I have to say about it, so it might be a little easier than one might imagine.
The other factor, which I mention in my paper and which is somewhat contentious, is the fact that if the provinces have the power to determine what a charity is, which is the constitutional matter, then the Income Tax Act could be amended to say anything regulated or registered by this council of the provinces and the federal government together is deemed to be a charity under the Income Tax Act. That would mean that if a province is not participating in that council, then the charities in that province could not get registered under the federal Income Tax Act. That's not to say it's a hammer, but it is a strong incentive for the provinces to participate.