Denti hits the nail on the head, as always.
SOPs should be SMS-driven for that particular operator. Of course feedback from other operators through OEM is valuable, but not everyone is operating in the same environment, and that means that SOPs will and should differ.
What matters the most is that changes in SOPs are based on solid (SMS) data, carefully thought out, and the tested via sim and line trial before introduction. This kind of approach, even if it deviates from OEM SOPs is much better than OEM randomly changing half of SOP, because someone whose operation is completely different, thought it was better.