The Wall Street Journal just ran an article about why shipping oil by rail is more profitable than shipping by pipeline:
Basically, shipping the oil by rail costs more, but using a train gives the oil producer the flexibility to ship to the refinery that will pay them them most for the oil. Shipping by pipeline only allows the producer to ship the oil to the refinery at the end of that pipeline.... and the oil producer has to commit to use the pipeline for a very long time.
Apparently, Warren Buffet figured this out years ago because he bought the BNSF Railway back in 2009. A BNSF train is shown in the picture attached to the Bloomberg article.
They've been trying to build one for years (Keystone XL) but have been stonewalled at every turn by Obama.
The WSJ points out that the proposed Keystone pipeline runs north-south, while the oil producers want to ship their oil east-west because the demand for oil is greater on the coasts than in Texas.