I've always seen DROP plans associated with governmental entities. Is it possible for a company to establish such a plan?

It would be very difficult, if not impossible, for a private corporation to adopt a DROP plan. Such an employer would have to work around the ERISA restrictions on back-loading of benefits. It would also have to make sure that the plan, as a whole, did not discriminate in favor of highly compensated employees. I have not seen one that has found a way around these constraints.