That is the current plan for the City of Toronto. The Toronto Transit Commission has just ordered 204 streetcars from Bombardier in the largest single order for light rail vehicles in the world. The contract is valued at $851 million CAD ($735 million USD, €523 Million).I also like what this article had to say about light rail and metro rail (like SkyTrain):
"The contract represents the largest single order ever for light rail vehicles worldwide and solidifies Bombardier's position as the world's leading provider of light rail technology," the company said in a statement.
New subway lines are extremely expensive and can cost over $1 billion per kilometer to build. They also require high urban densities and heavy passenger volumes to be effective.
Light rail lines are much cheaper to build and operate. They can carry higher volumes than buses, while creating virtually no pollution due to their electric propulsion. Light rail lines are usually built on their own right-of-way on street level, but can also be built underground in dense neighborhoods.