While the condescending tone is unnecessary, logicallee is right. There are actually zero links, Google just removes the quotes and shows results for that. None of them seem to have all the words together or the acronym. Just random occurrences of words on the page, and it's predominantly military documents.
That's because the military are actually really good at doing systems engineering, because it's all about writing requirements specifications, managing acquisitions and testing for delivery against requirements which is the military's bread and butter. Most of my experience in this area has been workign for ex-military people. NASA are also really good at it, and they publish a handbook on it which is very good:
They may not refer to the acronym "POSTED" exactly, but said acronym is what I learned and I thought highlighted the scope of what a system covers, specifically that it is not just the equipment i.e.: software. In the NASA SE Handbook, page 3 says the following, which essentially maps across to what I described:
"A “system” is a construct or collection of different elements that together produce results not obtainable by the elements alone. The elements, or parts, can include people, hardware, software, facilities, policies, and documents; that is, all things required to produce system-level results."
The problem is that the equivalent (US) military acronym is "DOTMLPF" - Doctrine, Organization, Training, Materiel, Leadership, Personnel, Facilities. http://en.wikipedia.org/wiki/DOTMLPF I'm a systems engineer that works for the military and I've never heard of "POSTED", it may be a NASA thing since they kinda have their own flavor of SE.
I'm AU and the guys I deal with are ex-ADF so I don't know. I'm glad that there's a wiki link for that one though, that helps when I next have to reference it :)
Same idea either way - the system is far more than just the equipment/technology.
I'm seeing one [relevant] link, an Australian senate hearing regarding the "Defence Legislation Amendment (Aid to Civilian Authorities) Bill 2006". This confirms my initial suspicion that it probably originated from some sort of military handbook - you can the pretty much tell by usage of the word "doctrine" alone.
EDIT: To be precise, I see [1], plus two mirrors of it, plus two links back here, but only from my phone. On my desktop I get zero results.
I favour (!) British spelling too but 'organization' is more correct in the etymological sense as it derives from the latin 'organizo'. The British form is in a way a corruption itself because it favours 'ise' as it is easier than learning the etymology. 'Oxford Spelling' is an etymologically correct variant of British spelling.