ATPL Validation
I just finished talking to TC in YVR prior to New Years on this same issue. I've been working overseas since 1996. As long as you maintain a valid foreign document, you will not need to write any exams. However we are still required to sit an instrument ride in Canada to validate the Canadian document.
What I've done in the past was to come back to Canada, rent a simulator for 4 hours and sit the ride. The IFR will be good for 2 years.
Hope that helps. Furthermore, I couldn't find the regulatory reference either, so I went directly to them. They were helpful.