Yes. If you have an active added year's contract, you can continue to pay into this on compulsory transfer to the 2015 scheme. Your added year's contributions will be paid until your contract ends and will then be paid as a separate benefit upon retirement.
NHS Pensions will write to you six months before the date of which the added years benefits are due to be paid informing you of your right to have them paid separately to your 1995 membership without having to leave pensionable service and continue paying into the 2015 scheme.