The article's title suggests an environmental basis but it quickly segues into the possible pitfalls for Trans Mountain's business case-prices could fall, demand could slacken .  
SO WHAT? 
Bombardier doesn't have a crystal ball either- no business does. 
The business case is not to be confused with the legal/ political case- should Trans Mountain be denied the right to access tide water by twinning its existing  line, and should Alberta be denied the right to access tide water that belongs to it as much as anyone else? 
As for the proposition that pipelines per se are evil- I will only point out that the author undoubtedly consumes  
products delivered by a pipeline everyday. 
My question re; Alberta's emissions- why is delivering millions of tons of coal to power plants by rail instead of delivering cheap, abundant, cleaner natural gas to them by pipeline? 
BTW; the approvals may stave off half a percent rise in interest rates. Without them the C$ would fall below 70 cents