Okay, so I'll try to post this as clearly as I can!
First, the times posted on CIC's website are *NOT* averages. If you want proof, just read what it says right on CIC's website (http://www.cic.gc.ca/english/information/times/perm/fc-spouses.asp):
The times are based on how long it took to process 80 percent of all cases between January 1, 2014 to December 31, 2014.
So that means that 80% of applications were processed FASTER than 29 months, and that 20% of applications took LONGER than 29 months, and that's just looking at applications received in 2014. In late 2013, London started processing applications from Islamabad. Previous to that, the stated 80% number for London was 11 months - which made perfect sense with what the spreadsheet was showing - 80% of applications filed via London were processed in 11 months or less. The average was generally about 6ish months in 2013.
Once London started processing Islamabad applications, the average dropped a bit, but only just a bit. British applicants, as well as applicants from countries that are processed in London (Ireland, Denmark, Sweden, etc), were still coming in at about 8-9 months from the time they sent their application to Mississauga to the time that they got Decision Made.
Applicants coming from Islamabad take, like, 2 years, hence London's averages suddenly being thrown way off. There are a few questions in the first part of the FAQ that address this. London's standard line is not to contact them for an update until you have passed their posted processing time... well, as soon as 11 months passed London started getting completely inundated with requests from Pakistani applicants, and it just completely flooded them - I'm surprised it took them as long as it did to change their published processing time!!
So it's important that when you consider how long your outland application will take that you consider the average for BRITISH applicants, and not PAKISTANI applicants.
So that's the first part explained.
Next, you know of Brits living in Edmonton who have had their PR completely processed in FOUR MONTHS, and they applied INLAND?! Sorry, I do not believe that for one second. IF they applied outland, then yes, I do believe that, the spreadsheet clearly shows that some applicants get processed that quickly, but I don't think anyone, EVER, has had an inland application get processed in 4 months. However, if they are saying they had their OWP issued in 4 months, then THAT I believe - CIC is trying to get work permits out to inland applicants within 4 months of receiving the application, so that is certianly possible.
Next.
The bit where you say the other poster said that applications are dealt with in the order they are received... that is broadly accurate. However, that does not mean that APPROVALS come in the order they are received. If CIC has two applications sitting on their desk, one received in January 2015 and the other received in April 2015, then they will open the January 2015 one first. But if the January one has, say, a messy divorce, lots of dependent kids, a hasty marriage, a big age gap, and lots of other red flags, whereas the one in April is just a simple boy-meets-girl-boy-marries-girl-boy-sponsors-girl-boy-and-girl-have-happy-ending application, then yeah, it's entirely possible that the April one will be approved in, say, 3 months, whereas the January one will be approved in, say, 9 months. So they will work on January first, but it does not mean that January will be approved first. Make sense?
(Stage 1 outland - the sponsor approval - goes broadly linearly and approvals come broadly in order because there are only a set number of factors that CIC looks at to assess the sponsor - criminal background check, are you on welfare, are you subject to minimum income, is the application complete - yes - next! - take a pretty set amount of time and there are far, far fewer variables at play when assessing the sponsor as opposed to assessing the applicant.)
Inland applications tend to be much more "accurate" in terms of posting times because Stage 1 is not as simple as just "approve the sponsor" - there's also a preliminary review of the rest of the application that takes place, hence it taking so much longer. In addition, applications filed from within Canada will be from a mix of all different citizenships and backgrounds - the chances of finding complicated applications in the inland pile are WAAAAAAAAAAAY higher than in the outland piles via Western offices. (Yeah, yeah, I know I am massively generalizing, but it's a fact!).
So my advice to you is this.
Read this article carefully - http://britishexpats.com/wiki/Spousal_Sponsorship-Canada - and pay particular attention to the bit about pros and cons of applying inland vs outland.
If you are desperate for a work permit, then apply inland. PR will take probably just over 2 years, but you will be able to work in a few months. If you are not desperate to work, are going to wait in the UK while your application is processing, or are content to chill out in Canada as a visitor for 8-9 months, then apply outland and have the whole process done and dusted way faster. Take the other considerations for inland vs outland into account as well, including freedom to travel in and out of Canada, as well as right of appeal, should you need it.
Hopefully that helps and is not too overwhelming. I'm heading off, but if you have more questions, I will be back tomorrow, or others will respond faster.
Good luck!