The WestJet flight off the tarmac at Kelowna was not landing, it was taxiing into position to be de-iced when it slid off the tarmac. I would assume very minimal (if any) damage to the aircraft.
http://www.cbc.ca/news/canada/britis...owna-slip.html
Actually had something similar almost happen me with them taxiing to the gate here at YYC a couple of years ago. Making the turn to line up with the gate you suddenly felt the whole plane start sliding sideways, the captain was quick on a reverser and stopped the slide, dumping a whole bunch of snow on the wing!