I can say that with respect to the UN High Commissioner for Refugees, that is their mandate. Canada is a signatory to conventions that facilitate and permit their access to our facilities. I have to admit that with the CCR, the arrangement goes back many years, so I'm not entirely sure of the origins, other than that they do offer their services as an independent group to government. This is an area where they have some expertise, so that's been leveraged over the years.
On February 14th, 2012. See this statement in context.