It is interesting to note that Bakken oil is competitive in newer markets, and that the price is now shifting back to par with WTI (or a premium in select markets).
When we started drilling in Elm Coulee back in 2000 the price was comparable (par) between WTI and the Bakken. As that field developed, the discounts went as high as $30/bbl due to transport costs.
That difference made other forms of transport economically viable--even preferable if the discount was even a few dollars lower--and as such, new markets have been reached where Bakken crude is competitive because of the price difference between imports and midcontinent oils.
I can see where Bakken crude could command a premium over WTI because of availability in markets where they were paying Brent prices for crude.
It is amusing that as an unintended consequence of delaying pipeline development, the obstructionists have actually improved the market for Bakken crude and possibly made it more profitable for producers.
I think this is key. Rail does allow them to get out of the Cushing Bottleneck. It is worth it to pay $5 more to ship if you sell for $10 more.