M & M conferences do not appear to be required. In 2+ years of working in firefighter positions, locums, and a permanent position only one facility had M&M conferences. That one appear to be largely dysfunctional and was opportunity to review any and all complaints. Approximately 90% of them were garbage that should've been addressed with a simple email from the medical director. Not sure what was up with it, however it seemed to be the local culture.
All of my colleagues that have been subjected to peer reviews (at least those that I know of) have been for for pretty suspect reasons. In the first, a nasty consultant made false allegations and referred someone to peer review. The ED physician was rather annoyed because in her view the consultant was blatantly lying. Other physicians had similar encounters with the consultant, however as he brought in a significant amount of money to the hospital and has significant political capital within the institution there never seemed to be blowback to the individual. The next two peer reviews I know of involved upset individuals trying to cast blame on another physician by preemptively sending a case to peer review and an attempt direct the narrative from the beginning and to deflect their involvement (and failings).
Via hearsay I only know of one peer review that seemed legitimate. Your mileage may vary, however I have a pretty jaundiced view of the peer review process.
Peer reviews are not a benign process, can easily be used for vendettas, and can affect your career.