For the record, I read an excellent article a few weeks back on this exact topic. (Don't remember the source though)
Basically, 50$/barrel is the break-even viability for the oil sands.
What the Saudis are deliberately doing is keeping oil-prices low in order to destroy the shale gas industry in North America.
Shale-gas, aka Fracking, is only viable with higher oil prices, at least 80$/barrel. That's because these are short term *get in there get out* entrepreneurial companies, with expensive startups. They're the ones whom are freaking out right now.
The Alberta Oil Sands, on the other hand, has always been a more long term investment plan. The startup infrastructure/machinery has long been in place. So, all they need to do over there is *wait it out*, hence some immediate/temporary layoffs... scaling back. But they're still in business. They're just scaling back their production/output for the interim.
Which sucks, because they are ultimately destroying the World.