Does the doctrine of mootness apply to appeal cases?

In Borowski v. Canada (Attorney General), 1989 CanLII 123 (SCC), [1989] 1 S.C.R. 342, Sopinka, J. for the court, held that where there is no longer a live controversy or concrete dispute, an appeal is moot. In Borowski, Sopinka, J. described the doctrine of mootness at 353. He said that, as an aspect of a general policy or practice, a court may decline to decide a case which raises merely hypothetical or abstract questions and will apply the doctrine when the decision of the court will have no practical effect of resolving some controversy affecting the rights of parties.