Sorry, but I've never experienced anything like that happening - there's always warning/cause for concern. The conditions necessary don't just spring in to being - there needs to be enough icy precip to overcome the ground warmth and accumulate (certainly enough time to adjust) or the ground needs to be very, very cold, which means long stretches of freezing temps and little-to-no sun... and then a freak rain storm moves in. I can't fathom what that would have to look like, meteorologically, but it can't be completely without warning.

It's far, far more easy to easy to explain a pile-up like that with negligence.