The other point perhaps that is missed in your comments is the fact that once they leave a minister's office and apply to the public service, these individuals are evaluated by the Public Service Commission. They must meet the criteria for entry, and they enter at a level in accordance with the criteria. It's not as if you leave a minister's office after three years as a junior staff member and you're deputy minister the next day.
On May 29th, 2006. See this statement in context.