http://www.cbc.ca/news/canada/windsor/story/2013/03/12/wdr-p... It sounds like it's mostly little clumps of carbon, so it should be more-or-less harmless?
My interpretation of the CBC piece was that is that pet coke is non-toxic so long as it doesn't become airborne or fall into the river. Once it's in the air, it has the same polluting qualities as anything else that can stick in the lungs. How fast can they get it in a tanker and get it to the folks that would turn it into asphalt? Could that be... faster? Too bad the stuff isn't activated charcoal. We'd have more than enough to filter cheap vodka through it to make good vodka. Then it'd be time to get it into barrels and start making Popov Select or Mr. Boston's Brahmin Touch. Mounds of coke waste sound like a problem from the 17th Century, the kind that led to the urban prominence of London Plane trees.