Hello, you are close with your question about how cases are prioritized. When I was more in tune with things it worked this way:
Priorities begin with PRRA cases, so this includes mostly failed claimants but includes any PRRAs because there's a removal order and an impending removal. The CBSA and IRCC have corresponding priorities because they're two parts of one thing, the Canadian public service. IRCC feeds the CBSA removal process PRRA decisions for the people who took up the CBSA's offer for PRRA.
If you have a PRRA then your H&C decision will become a part of that premier priority.
The priorities within this over-riding principle are criminality and security cases. There are not large numbers of these so it's something of an overreach to say that this dominates the pace of decision-making.
But, how do they organize their case distribution?
They distribute their casework in groups identified by nationality. What I mean here is that an officer gets 5 cases from France (for a neutral sort of nation in order to avoid any offence). Another officer might get 5 from Antarctica. There could be a variety inside of this "pocket," and what I mean here is that there may be 2 with only a PRRA, and 2 with a PRRA and an H&C and one lonely H&C without a PRRA - all from the same nation.
People rightfully remain incurious about budgets, workforce levels, grades or ratios of decision-makers to clerical and administrative staff. But along with these things that the Government has to consider, they also have to maximize their output. Targets for individual decision-making are intensely reviewed to see that the decisions are being pumped out. Statistics are always a topic of interest both by office and officer.
So, thick files, thin files, this or that - you look at the whole inventory (PRRAs & H&Cs), you distribute the inventory in such a manner as to keep the CBSA PRRA decisions moving, then try to filter down the H&C inventory by its age (not letting them get too old while juggling the other stuff).
There's incredible repetition inside of certain casework, and so assigning multiple cases from distinct countries speeds research and familiarization with the issues in those collective files. This way you get officer expertise, more rapid decision-making and greater statistical output.
When I knew what they were doing this was how they did it. Have they changed or screwed it up since then? I wouldn't know. I can tell you that about 10 years ago their training told them when they had a PRRA and an H&C they should look at the H&C first because they have greater discretion with an H&C. If they say yes then the PRRA's immediately refused and you move on.
There's plenty of tension and apprehension and speculative worries when people reach this point in their immigration odyssey. It should help to know that there isn't much attention paid to trickery.