I'm one of the authors of the trauma-informed peer support curriculum guide that Robert Olcott refers to above that appears on the NASMHPD website and was developed under SAMHSA's National Center on Trauma-Informed Care. With one of my co-authors, I also provide trauma-informed peer supports (TIPS) training as a consultant.
Intentional Peer Support, developed by Shery Mead, which Robert Olcott also mentions, is a wonderful peer support training, but it doesn't specifically focus on trauma-informed approaches.