I've seen that 1.5M number bantered around lately. Seems about right if you take in the network of towns in the vicinity of Ottawa-Gatineau. Just the way (south) Central Canada is. Now, if Ottawa could get a skyline to match that number...
So we have the big three (Tor, Mtl, Van), the next three (Cal, O-G, Edm), and the next three (Q-C, Wpg, Ham), and the next two (K-W, Lon), and after that the next four (StCat, Hal, Vic, Wind), followed by the next three (Stoon, Reg, Sherb)