Research is currently being conducted on this population so the only reports are currently anecdotal.
An EMDR protocol for this population was developed by Marcia Whisman [314/644-1241 x3] who has extensive background in the cognitive-behavioral model of anxiety disorder treatment. She reports that her clients are being successfully treated without the need for therapist assisted in vivo exposure. She has presented her protocols at numerous EMDR conferences and has received excellent feedback from her trained clinicians.
I believe that the rate of success is high, but it is not as rapid as EMDR treatment with other populations -- although still reportedly faster than with other methods. It is interesting to note that years ago it was reported (Rothbaum, 1992) that there appears to be a link between tracking deficits and non-reponsiveness. Specifically, there is a metabolic abnormality of the orbitofrontal cortex in this population that may inhibit information processing, and therefore be responsible for the slower success rate (Baxter, Phelps, Mazziotta, et al., 1987; Rapoport, 1989). However, as you suggest, the integration of EMDR within the cognitive behavioral framework appears to be greatly enhancing treatment.