IFR Renewals
This is a two sided issue:
1. In order to keep a Canadian ATPL alive and usable, the document holder must sit an IR Ride by an TC examiner, every two years.
2. If you do not sit the IR AND you do nothing else, the exams go 'stale' and you have to sit the INRAT again.
The answer to not having to sit INRAT is to keep a valid foreign ATPL with the corresponding documentation (License skill test/license proficiency check) valid.
If the Canadian document holder does not wish to sit an IFR in Canada and maintain a valid ATP exam set, all he/she needs to do is maintain a valid foreign ATPL and present TC with the documentation prior to presenting themselves for a Canadian re-validation.