No, that is not possible. There are provisions within Industry Canada's spectrum policies.
Under the current roaming policies, under spectrum conditions of licence, it's a requirement that the carriers provide roaming to other carriers. They cannot be refused.
That was put in place in 2008. In 2013 the government extended those provisions indefinitely. In 2008 they were set for a period of time; in 2013 they were extended indefinitely.
So, no. It is a requirement under those conditions of licence.