What is the best tree or shrub for a privacy screen in southern alberta?

An upright evergreen will give you year around privacy. There are a variety of upright arborvitaes that are fairly fast growing and would work well. The exact type depends on the width and height you are looking for at maturity. They give you year around color that a large deciduous shrub or small tree like the Amur maple , will not give in the winter.