I think they started showing the background check in progress straight away after SA for applicants whose apps went to Mexico after mid-January. The theory is that they started processing the background check in Mississauga, hence after I received SA on March 3, my GCKey account was showing "Your background check is in progress ...." and I never saw the message "Next step is to conduct a background check". However, I don't know for sure and if this is the case what exactly they have done for 3 months now and we have not gotten any requests for another PCC from Canada, which I was expecting if they are to complete our background check. Our eligibility also changed to in progress at this time, and is still showing this. Again, I don't know where they are at with that either. Our last correspondence from the VO was on May 26 when we got the email for AOR2. However, on May 4 we saw a fourth line on our eCAS that indicated "We started processing your app on May 4", meaning that was when they opened our file finally at the VO.
As Sneaky said, the only way to know what is really going on is to order GCMS notes. It seems that this is a new procedure they are starting, probably to help them process the apps according to the new standard of completing processing of 80% of the apps within 12 months. So I think not many people out there know what might be happening with the background check since it's a new thing.
My plan is to wait until the end of the month to see if I get any requests, if not, I'm ordering the GCMS notes at the end of this month.
Hopefully you hear something from them and won't have to go this route.