It's the same process for any regulated entity seeking an exemption. There would be an application made to the responsible minister or regulatory body. Depending on the jurisdiction, it could be the minister responsible for accessibility, it could be the minister of transport, who is responsible for the Canadian Transportation Agency, or it could be the CRTC. The public service would then provide advice to the minister responsible on whether that exemption, and the basis for that exemption, were founded. Then there would a determination by the responsible minister or the responsible body, and that exemption must be published, for transparency purposes, in the Canada Gazette.
On October 2nd, 2018. See this statement in context.