Party politics aside, when it's that much money, that large a part of the economy,

anything that isn't there to grease the wheels is likely smoke and mirrors.

First a disclaimer, I know Palin's a troll, OK? But remember how Sarah Palin was ridiculed for "drill, baby, drill!"?
Considering events post-2007, it's clear that she was just saying it as it is in any case, regardless of what this or that politician says in a campaign.
That was before fracking became the solution to a hell of a lot of problems for the US. And that didn't happen under Sarah's rule.

At the current price of oil and gas the Canadian tar sands are hardly economically feasible.
http://www.torontosun.com/2015/08/20/most-canada-oil-sands-crude-being-produced-at-a-loss-report
"CALGARY - More than three-quarters of Canada's daily output of 2.2 million barrels of crude from oil sands is being produced at a loss at current prices, research from analysts at TD Securities shows, although producers are unlikely to halt operations."

At present, the pipeline isn't immediately necessary for anything to do with making fat profits. The industry probably doesn't mind, at all, putting the project on hold while more profitable and less politically sensitive or well known endeavors are pursued.

By the way, when I just looked it up it seems that "tar sands" is a controversial term and some prefer "oil sands". But that's just image. What is it? "Oil sands are a mixture of sand, water, clay and bitumen", and way back in the long ago when I was a kid I learned that "bituminous coal" the dirtiest and lowest grade of all the coals, far and away inferior to anthracite. So what we have in the Alberta "oil sands" is a sludge of clay, sand, mud and bitumen, which has to be combined with water and a whole shitload ofheavy duty chemicals to turn it into a flowable soup before it can be passed thousands of miles down a pipeline - and all of this has to be processed at the end of the line before it can be sold as some kind of oil product. These products are necessary - oil, gas, plastics, and more - but really, putting Keystone on hold was a no-brainer.