That's a very good question.
Unfortunately, the government is very tight-lipped about this. I can tell you that previously when we, as CBSA officers, were using the system to do security checks, it was very.... Back in the day, they had this system called FOSS. It's a similar system to CAIPS, the global entry system where they prepare the files.
For the CBSA, when we have refugee claimants or typically for work permit applications that show up at the border, this process is actually not done, the security checks. A lot of times you can ask the applicant to show up with a police certificate to satisfy yourself that they don't have any criminality, but on the security check itself, the government is very tight-lipped.
Even at the officer level.... There were two boxes that we had to click to ask for security checks. One was to CSIS and one was to the RCMP—sorry; there was a third one to go to the CBSA. We, even as officers, didn't know exactly how this process worked. Eventually we would get an automated message on these ones, saying “security passed”.
I couldn't shed any further light on those, especially for the PR process and what the background checks look like. However, at the border when somebody comes to do their work permit application, this is not actually part of the regular process. The extent to which you can go is a police certificate, and that should satisfy you about criminality, if not security clearances. There could be somebody, let's say, from a terrorist organization who shows up. Unless for some odd reason they show up in some sort of a system that the CBSA would have access to, you wouldn't actually know.