There's no pre-requisite. Any Canadian citizen, permanent resident, or person currently residing in Canada can request them. Canadian citizens and permanent residents have the *right* to receive the ATIP information, so I would recommend the sponsor submit the request with a completed and signed consent form from the PA.
However, I think you're unlikely to learn anything new and significant unless you know that they are having problems with your application (e.g., you received an ADR or PFL, or your application file got transferred to another VO for further assessment).
I ordered GCMS notes for my husband's application (he is the PA, and I am the sponsor). We were getting impatient because our eligibility had not started (we applied in early June; it still hasn't started as of today, Nov 12). The only things we learned were that my husband had passed criminality and info sharing with the US was in progress.