Put yourself in the shoes of the brain trust at national campaign HQ. If you are going to do a black op like this you want as few people to know about it as possible, and that they be th emost loyal. The logical place to plan the logistics is in the riding campaigns. But that means way too many people involved. That would not be the rule, and the Guelph case may even have been a freelancer who heard about what was going on.
Even planning and running this out of national HQ would involve a lot of people and be heard of by quite a few more. It would make sense to contract this out to a small frim of loyal Conservatives.
Yes, this is a logical surmising of what may have happened. It once again relates to the concept of Plausible Deniability.
The best explanation and dramatization of Plausible Deniability that I have seen occurs in Oliver Stone's "JFK" in the scene with Donald Sutherland's 'Mr. X'. (Sutherland is of course the father of Keifer Sutherland, the grandson of Tommy Douglas! )
As 'Mr. X' explains, in this case involving the Kennedy assassination, when you have plausible deniability the goal is to make sure that no one in the power structure hierarchy knows anything about the specific details of the operation. As he states, "There are no compromising connections, except at the most secret point."
No vote has been taken, nothing's been written down on paper, but everyone knows what the objective is - Kennedy must die. Someone in the chain is chosen to arrange some of the details of the operation, and someone else is chosen to arrange another aspect of it. But no one person knows exactly how it was arranged.