We deal with a few governmental money purchase plans whereby if an employee elects to voluntary contribute some additional money to the plan, it must be done on an after-tax basis.

Could a ROTH 401k be added to MPP?

If the money purchase plan is a 401(k) I believe that you would be able to add the Roth component. However, a vast majority of the money purchase plans in Pa were not grandfathered and there are very few (k)'s in effect.

If the tax deductability for the voluntary contribution is important, why wouldn't they just use a 457 plan?

457 is an option, of which is already in place.

The ROTH is a hot topic in the corporate world and I wasn't sure how it translated to a MPP.