From all I've read, my situation is more unique than most posters. I applied to sponsor my common law partner (same gender) while living outside of Canada (in the US on a temporary work visa). We got scheduled for an interview on September 9th of this year at the LA office.
I ordered the GCMS notes and got them after a month. I found out that the reason for the interview as to A) confirm that I would be moving back to Canada upon completion of sponsorship, and B) because our relationship had started in some form of Polygamy, and they wanted to ensure that was done and over and not going to happen again.
Our relationship was 3-way to begin with and did include a female counterpart originally (I was an addition to the existing male/female relationship), but that aspect dissolved and we ended up going our own way 5-6 years ago. When preparing our materials for the interview I made sure to provide this information up front, along with assurances that we had no intention of trying something like that again. Along with that, I included all requested official documentation, additional declarations of our relationship being genuine from mutual friends, updated lease and insurance records, updated shared expense items (mainly me paying for events/flights/etc. for my partner), and other updated relationship supporting material.
The Interview:
We arrived at 8 AM on the interview date for our 9:30 AM appointment . The couple who were there ahead of us were apparently a complex case and took up a great amount of time. We got ushered out of the office for lunch and were asked to return at 1 PM for our interview, though it didn't actually start up until more like 2:30 PM.
Our immigration officer was a female of Asian descent who was very flaunt in English. She apologized for the long wait and seemed in good humors overall, despite the complex case that came before us. My partner was called in first and got the bulk of the questioning, about 30 minutes I believe (see below for details). She played with different dates a lot, misquoting 'first met', 'relationship start', 'first visited', 'moved in' and 'moved out on our own' numerous times, and requiring my partner to correct her constantly. I think this was intentional, to make sure the story stayed straight, so if you have a poor head for dates and numbers, I recommend you brush up on that knowledge toughly before your own interview. Once that was done, I was called in additionally and the pair of us fielded some joint questions for 15 minutes (also see below).
At the end, the officer said she was satisfied that we were a committed and exclusive couple and she would be approving our application. She wasn't able to provide an exact estimate on when it would all be done because the redone medical exam still had to be reviewed by another department, along with the redone criminal certificates. She did say she was going to ask us to sign a declaration of common law union, and that would be taken care of later.
Aftermath:
The next day we received an e-mail asking us to complete and notarize an IMM5409 form / Statutory Declaration of Common-Law-Union. We completed that within a few days and sent it off by registered mail back to the LA office.
About a month later (Oct 7th) we got another e-mail stating that my partner's medical results were in, and that the application could now be finalized. They requested 2 passport sized colour photos per Canadian passport standards. My partner got those done and sent them off to the LA office via registered mail once again.
Exactly one week later we received a piece of registered mail from the LA office that contained the finalized documents that permit entry into Canada as a Permanent Resident (yay!), along with instructions on how to cross the border and other general 'settling in Canada' information. The documents are good for about 1 year, and we plan to make our trip up there come March.
We started the process/submitted our documentation in May of 2013, and the process is now concluded as of Oct 2014. Best of luck to everyone still waiting, and I hope my information provides some help for you.
Questions for my Partner:
-when were you born? where?
-who are your parents?
-do you have any siblings?
-when did you first meet your partner?
-when did your relationship start?
-when did you move in with your partner?
-describe how relationship developed
-who pays for rent/utilities/insurance/etc?
-who does the cooking/domestic chores?
-so you are the 'female' of the relationship?
-when did you start liking males?
-what will you do if your application is not accepted?
-have ever been with another male? has your partner?
-where will you live?
-what does your partner do for a living?
-do you trust your partner? how do you know he won't leave you as soon as you're in Canada?
-are you married? why not?
-have you met your partner family?
-do your parents know of your relationship? why not?
Questions that were posed to both of us together:
-where will you live in Canada?
-what do you (me, the sponsor) do for a living?
-how will you (my partner) explain going to Canada to your parents?
-where do you see this relationship going?
-why didn't you get married? why didn't you visit Canada to marry?
-will you get married?
-what will you do if this application is rejected?
-are you in a committed monogamous relationship?
-will you (me, the sponsor) be returning to Canada?
-why didn't you get married/registered as domestic partner in order to help this application process along?