Few days ago, i wrote a huge answer but it got f*** erased.
What bijoy said also applies for ALU. The 8PSK is levelled only if the GMSK is attenuated by parameters (BS TX PWR MAX). The goal is that the 8PSK never gets stronger than the GMSK.
In ALU, you cannot decrease the power of 8PSK only. The only parameter is BS TX PWR MAX, which acts on the GMSK power. And under condition explained above, it will act on the 8PSK.
Basically, the operator has nothing to do, it is all automatic.
The only thing is if you have a cell that contains only TRX for older generations (all TRX are TRAG/TRAD or older, without even 1 TRAGE or 1 TRADE). In this case, the 3GPP recommends to set the BS TXPWR MAX to -2dB.
(This is a matter of RxLev mesasurements from neighbour cells) (it is not critical, most operators don’t really care)