I see some books have started offering Interac E-Transfer as a deposit/withdraw option for Canadian accounts.
I know Sportsinteraction & 10bet definitely offer this option to deposit and withdraw.
Also, the "MuchBetter" app/ewallet also accepts deposits via Interac E-Transfer and you can use it at Pinnacle, Betway, Bet365, Sportsinteraction, 888sport/poker, Pokerstars etc. You can also take a withdrawal from Muchbetter via Interac E-Transfer.
E-Transfers take approx 30 minutes (sometimes faster) from the time they are sent until you receive the email notification funds are available. You can also setup "autodeposit" by registering your email address in your bank or credit union E-Transfer settings and then the funds will be deposited automatically to your bank acct.
If you know of a book that accepts E-Transfer please post it here.