It certainly does seem that they at least release the notifications in batches, given how many people received the medical request at the same time, and how many were transferred to CPC-M at the same time. But apart from that I don't know how much we can read into their processes. A lot of people were in fact transferred to CPC-M who
hadn't completed their medicals yet, so I don't think there is actually a correlation there. My hunch is still that I am being sent (or have already been sent) to the local VO, the notifications for which are a lot more spotty. I guess we'll find out if we get included in the next batch of notifications or not!
Are you (i.e. the sponsor) living abroad? If so, I suspect you'll be in the same boat as me. If you're in Canada, then I think you still have decent odds of going to Mississauga in the end after all (especially if your GCKey is already showing background check in progress). As usual, these are just my guesses though!