Seems to me the main rationale for building a pipeline was that it would enable exports of crude and bitumen to get to markets where they’d sell for a higher price, meaning it would be more expensive for domestic refineries too. There have been quite a few news stories in the past year suggesting it’s had some success in doing that. I don’t know whether that effect has lived up to expectations, but it’s an odd thing to not mention at all in an article discussing the effect of the pipeline on gasoline prices.