“Enhanced Full Rate or EFR or GSM-EFR is a speech coding standard that was developed in order to improve the quite poor quality of GSM-Full Rate (FR) codec. Working at 12.2 kbit/s the EFR provides wirelike quality in any noise free and background noise conditions. The EFR 12.2 kbit/s speech coding standard is compatible with the highest AMR mode”
There is no impact on your BSC, but maybe you ought to check that your Transcoder (TC) is compatible with this voice codec. However i believe it is a standard feature for a TC to support EFR.
The only benefit is to improve the voice quality as compare to the basic Full Rate codec. Subscribers will benefit from hearing a better voice quality.