DND writes a spec sheet, specs that explain in great detail what this piece of equipment needs to do, it is then given to PWSG, who are all civilians, no military at all, they then go out and pick several pieces of equipment that THEY think might fit the bill, DND tests them, discloses all the faults what they like or disliked, then the whole file gets taken up stairs to the politicians and they have the final decision, and as argus has explained the key factors are off setting "what can the company do for Canada, in most cases the company is asked to spend the equivalent of money in Canada...