The nRF51 Series Reference Manual v3.0 notes the potential need to set the OVERRIDEx registers in the radio mode to values from FICR.BLE_1MBIT to meet deviation requirements for BLE (per PCN-083 rev 1.1). FICR also contains override settings for NRF_1MBIT. Examining a selection of four chips, most have the NRF as well as the BLE bits cleared (i.e. do override) in FICR.OVERRIDEEN.
For an application that uses multiprotocol S110 BLE and Nrf_250Kbit, I understand S110 will automatically apply the BLE overrides. Is there any issue with leaving those in place when operating in Nrf_250Kbit mode?