I do not know of any research on countertransference and mentalization per se, let alone trauma, mentalization and countertransference all together.  That would be interesting to do!  As far as trauma and mentalization, we have two papers:  Schechter et al., 2005 in Attachment & Human Development and Schechter et al., 2006 in the Infant Mental Health Journal with a follow-up study that is related in Child Psychiatry and Human Development, 2015.   There is also the study by Diamond et al., 2014 on Narcissistic and Borderline Personality Disorder and mentalization.  I would look at the Mentalization-Based Treatment (MBT) papers by Bateman and Fonagy, and case related  reports (a recent one by Roussow, 2015). 

We have develop a mentalization based assessment of countertransference in relation to borderline pts which can easily be used with material from pts with trauma (the measure is described in our article on whether therapists can be trained to be more reflective). We also have the article on trauma and mentalization suggesting that it is very important to tap mentalization specific to trauma (and I assume this might apply to therapists as well.

My PhD-dissertation touched on this topic. It is a systematic single case study of vacation breaks in a 4-year-long child psychotherapy with a child whose early relationships were reported emotionally traumatised and unstable. The study applied qualitative methodology to analyze case notes, semistructured interviews with parents, and casefiles.  Among other dimensions, the relationships between countertransference and the child's ability to symbolize and learn were studied. Reference:  Grünbaum, Liselotte (2014): A Study of Anxieties and Dilemmas Relating to Breaks in the Therapeutic Relationship with Children Whose Relationships in Early Infancy were Reported to have been Emotionally Unstable and Traumatised: A systematic Study of a Young Child who had suffered early abuse and neglect. University of East London Institutuiona Repository/The British Library EThOS