Since most Canadian federal government employees have only been able to accumulate miles since June, I expect the current number is pretty tiny since you would need to be doing serious flying to have already reached SE, or be someone like AC*SE who travels a lot for pleasure. The number will, of course, ramp up, particularly next year, making the Ottawa MLL a busy place and making upgrades ex-YOW significantly harder to get.
MPs, Senators, hangers-on, provincial govt. employees, Crown corporation employees and so on I suppose could already be SE. If all MPs and Senators are SE, that represents about 5% of the total.