I conduct trauma focused cognitive behavioral therapy will children. I have begun including play therapy in my sessions. I have not been able to find sufficient research studies on play therapy and trauma.
I have not conducted any research or a similar research of this kind, especially with children. I have been working with some elderly with cognitive behavioural impairment, where I have seen play and humour enabling some access to reach out to them, especially when communicating with them became very challenging.
You can take a look at the links attached here which I believe would serve a great purpose bringing you to a desired goal.
Developmental Play Therapy in the Treatment of Childhood Trauma
Play therapy is a quite generic term and covers many different types of interventions for children. Given your interest in CBT you might fine reference to therapist directed play therapy.
You might take a look at 2 studies on the web by Esther Cohen and myself. The Children's Play Therapy Instrument has an adaptation for trauma. (CPTI/ATR)