Key line: "The company did not specify the reasons for its decision in Thursday's announcement."

So, let the speculation, the innuendos, the guessing games commence. 

My question is, why not specify the reasons? Here's speculation of my own: the bottom line (forgive me) is that Trans Canada is in business to make the most money with the least resistance and cost. "Nation-building" (thank you, Premier Notley) is not high on its priorities.  This is bad?

So--more speculation--it could be that TransCanada has plans in quite another direction:

"Balls of bitumen: Calgary breakthrough could bypass pipeline problem, researcher says" (CBC Sept6 2017)
And, 
"Oilsands crude pellets touted as cure for industry's bitumen transport ills" (Financial Post; Toronto Sun)
And,
Calgary professor thinks oilsands crude pellets could be cure for industry’s bitumen transport problems" (Globalnews)

Name change, maybe? TransCanada Pipeline & Rail?  Ya never know...