This has almost nothing to do with Keystone. It is about a cartel (OPEC, but more specifically Sauda Arabia) attempting to drive competition out of the market. They are attempting to protect market share. Besides, many Canadian producers are now using railcars to ship crude when there exists pipeline bottlenecks.
Since I'm too lazy to write a summary of the break even costs for oil production in N.A., here is a picture instead. Canadian producers are relatively secure at the moment because of the depreciation in the CAD relative to the USD.