I doubt society (Canadian in general and BC in particular ) will see a net gain? All this will serve is, as has been pointed out a direct route to China of Oil that would otherwise be on the market and subject to the ups and downs of the rules of supply and demand. Nothing more!
The tar will also be processed without responsible environmental guidelines and used to power industries that are also less than environmentally responsible making goods that will then compete on the open market with goods produced under stricter legislation. In affect we are supporting the lowering of environmental standards and the welfare of working people. Instead of forcing the Chinese or? to raise their standards, we are rewarding them for not doing so.
Not to say anything of removing this oil from the NA market and therefore the localised rules of supply and demand will allow for Big oil to reason price hikes.
This will be also a way for the US, to have some control and/or have leverage over China. China is making private deals worldwide for it's commodities and is bypassing the system of fair market demand. Akin to the Log situation and coal of the eighties.
when or if this pipeline is built and hope not, The US will add it to the list of Strategic needs and use all the power required to control it. Do not kid yourself that WE Canadians will have any say on it's use.
http://www.strategicstudiesinstitute.army.mil/pdffiles/pub705.pdf