I do not have any first hand experience and would believe that if they can digest teeth, jawbones, nails and hair, then fiber should be no issue.

On another forum I use to frequent, there was a thread with pictures of a neonate that swallowed a wood chip which was much wider than itself. On it's way down, it went crooked. The general consensus of the forum was to get to a vet ASAP so it could be surgically removed and if that was not done, the snake would surely die of impaction. Instead of following the forums advice, the owner massaged it so it was going down square. On top of that, he fed the snake.

That member caught all hell for doing that and was told the snake would die.

I think that was the gist of it. In any event, the snake was just fine. I'll see if I can dig up that thread if anyone wants to see it.