Smells a lot like an inside job to me. They knew the trial would lead to them and they had the evidence that could sink them. Stage a burglary and get rid of it. The mob would have just busted it out and started a fire.
Agree that it smells like an inside job. There is no PR firm privilege that would protect them from disclosing client confidences if subpoenaed for the data. So the information had to be destroyed.