You're correct that there is the choice built into the framework for the PRPPs. There is the choice at the front end, where the employer chooses to join, where the employees have up to 60 days to opt out altogether, and even if employees do not opt out at the front end, if their circumstances change at some point in their employment—they might be facing financial difficulties or whatever—they can choose to set their contribution rate to zero for a period of time to allow them to get through that, and then at a later date increase their contributions again. There is that choice that is built right into the framework.
On February 16th, 2012. See this statement in context.