The rules can vary, depending on which country, and even between different Airports in the same country. In the UK, for example, the 'norm' is to not issue a landing clearance until a preceding departure is airborne. However, at London Heathrow (and some others), under certain specified conditions, a landing clearance may be issued before the departure is airborne.
NavCanada will specify the rules and conditions for the issuance of a landing clearance in your home country.