I think that more than anything it depends on your individual case. The time it takes for the officer to review your files and documents will obviously depend on how complex your situation is, whether you have accompanying/unaccompanying spouse/dependants, how many countries they have to get security and background clearances from, how much time it takes for them to request additional documents from you, and so on.
Also, at the end of the day it may come down to small things and coincidences, like public holidays when the officers aren't working, or them getting sick and their work piling up, or just different working methods between individual officers. One really can't draw any waterproof conclusions about timelines, because there are so many variables. Personally I'm looking more at AORs than IPs, just because to me that seems to be a more solid milestone than IP.
So if you got AOR at the same time as someone else, and they have IP and you don't, then it may be that they get their PPRs earlier than you (provided that their processing goes smoothly), or it may be that you get yours first (if your case turns out to be more straightforward than theirs).
But then again, we've seen here on this forum that CIC tends to roll out PPRs in batches (like applicants of a certain month), so it may be that the early IPs end up getting their PPRs at the exact same time as the later ones.
It's all kind of chaotic and unpredictable. We'd all probably be better off not following each other's timelines too closely, it makes you all jittery and paranoid... but I guess that's part of the experience...?
