Watched this live on the internet last night - man that's a tough one. I would not be able to ride 10 metres in some of those sections! I wouldn't be fit enough to manhandle the bike, let alone have the skills.
After an hour and a half of riding, the lead guys got stuck in a nasty slippery little uphill section. I watched for 40 minutes as they worked with each other to pull/push the bikes up the hill. When I gave up and went to bed they'd managed maybe 20-30 metres. I'd have needed a defibrillator and oxygen well before that point.
I read that they all shared first place so I assume once they'd made their way up they stopped racing and just rode to the finish.
Very sporting indeed! But one helluva race.