I am not an attorney, so I don't know what the rules are regarding destruction of records in anticipation of subpoenas; but I would suggest that this happens far more frequently than the article implies.
One possibility I can think of is that when the news about Enron broke, the audit staff on the Enron account took it upon themselves to dump records. Whether that should have been prevented by senior management at Andersen is something that should be looked at.
But I've never been involved in a situation where my own conduct couldn't stand the scrutiny of a court. I think it's entirely possible that if I were, I might rationally decide that destroying evidence of wrongdoing might be the best course of action. Let the company take the heat and personally deny, deny, deny.
My hunch is that this is exactly what happened here.