Thank you for the question.
Currently, under the National Energy Board Act, a pipeline certificate holder can apply to abandon a pipeline and the board will hold a hearing process and determine whether or not a pipeline may be abandoned and will issue a certificate for abandonment. At that point the federal government and the National Energy Board's responsibility would end and the pipeline would be abandoned in place.
Typically, industry may pursue options as to how to deal with abandonment. They may take the pipeline out of the ground, but more often than not, pipelines are filled with sand or cement or some other inert substance that would simply leave the pipeline in place.