I'm guessing that a shank would be someone crashing and a mulligan is if someone didn't like their run, eventhough they didn't crash, and wanted to try again.
I'm thinking that every rider will be given one mulligan to use at any time throughout the comp on any "hole" that they did not like their run. Sounds pretty bad ass. It will be nice to see people in the BC competing and pushing themselves with so much talent around.