For CAD, assuming someone from Canada, ATM exchange rate is 2.5 - 3% . Even with the "poor" (compared to USD/JPY.. ) exchange rates in HK, it's still way better than using ATM. Chung King Mansions and Berlin only charge ~0.5% . If you don't have a fee package, each ATM withdrawal costs 5CAD on top.

Only some obscure Canadian CC do not charge currency exchange fees. Again the norm is 2.5 - 3%.