What goes unstated in this debate is that this plan while certainly increasing the capacity of the existing line also effectively replaces the the existing line which is now over 60 years old, built in the early 50s with 1940s technology.  The new line will be state of the art and therefore orders of magnitude safer than the existing line.  With the new line completed the old can be shut down and effectively replaced, likely in segments over time.  Should the new line not be built the existing line will eventually fail in a big way or will be forced to shut down likely for at least a couple years to allow for its rebuild.  In either scenario BC loses big time.