I can try to answer, but in general - it's hard to know what is happening, as it's more "inside CIC" and each VO is a bit different!
Some VO ask for the passport upfront - Manila, New Delhi for example - so being asked for the passport is not a sign of being read to have a PR issued... while some others (London, Ottawa, Rome, Bucharest) ask for it at the end of the process, so once the passport has been requested, it's the end of the process.
The second stage is focusing on the applicant (stage 1 is about the sponsor): background checks, and trying to establish if the relationship is genuine or not.
Background checks depend on the countries - some take a few days, others are quite lengthy... if the applicant comes from a country which has seen war in the recent years, it will take more time as CIC will want to check the background more extensively.
Relationship : if it's a straightforward case, then it can go quite quickly. If previous children are involved, or second marriage, etc, then it takes a little bit more time.
About who handles it - I don't know. most likely the file is assigned to an officer, and if the case is not too complicated, then the officer handles it. If it's complicated, then a senior officer might review it as well.
Part of the waiting time is also just waiting until somebody is assigned to the file and it's being looked at and assessed - there is a "queue" at most VO....and most officers will handle several files at the same time (starting one, and asking for background checks, then working on another one until the background checks come back etc.).
Good luck,
Sweden
