Yes. If you have an active additional pension contract, you can continue to pay into this on compulsory transfer to the 2015 scheme.
If you are a member of the 1995 section, NHS Pensions will write to you six months before the date of which the additional pension is due to be paid informing you of your right to have the benefits paid separately to your 1995 membership without having to leave pensionable service and continue paying into the 2015 scheme.
The above provisions do not apply to the 2008 Section because continued pensionable service in the 2015 Scheme after taking benefits from the 2008 is permitted. Further, additional pension taken after your 65th birthday in the 2008 Section is subject to an actuarial increase to reflect the fact it is taken later.