In general, the more firmly denied or deeply buried in our psyche something is, the more forcefully we may project it onto or into another person. So of course dissociated projective identifications are especially forceful. They frequently are very disruptive in our lives as multiples and important in our psychotherapy treatments. For example, here is a long quote from a book for therapists, edited by Drs Richard P. Kluft and Catherine G. Fine (1993), "Clinical Perspectives on Multiple Personality Disorder", Chapter 4 by Richard J. Loewenstein, "Countertransference in the treatment of multiple personality disorder", p.66-67:
Because of the intensity of the dissociative projective identifications, the therapist may also experience altered perceptions in work with MPD patients. These often-disconcerting phenomena include intense imagery, often with a sexual or aggressive content, negative hallucinations, depersonalization, trancelike experiences, countertransferential "spacing out" and sleepiness, and inability to think. Obviously, therapists must be extremely rigorous in accounting for their own idiosyncratic countertransference contributions to such phenomena. Also, it is critical for the therapist to inquire neutrally and tactfully when experiencing in the countertransference disquieting sexual or aggressive imagery that seems to be evoked projectively by the patient.
For example, I had the following experience in my early work with an MPD patient who had previously become overinvolved with several therapists. During a fairly routine session, I momentarily became flooded with an insistent visual image and tactile hallucination of touching the patient in an intimate manner. Although I felt intensely disquieted and disoriented by the experience, I managed to inquire neutrally if "something had shifted" within her at that moment. She replied: "Yes, the sexy one is here now. And do you know what? She's a child!" As this personality emerged and began to talk, my hallucinatory experiences ceased.
We were then able to discuss more openly various alters' fears that I would become involved with the sexual alter, who would be unable to refuse my advances. Also, we were able to discuss this alter's previous exploitation in several prior therapy and nontherapy relationships. The patient's more executive alters had been unaware that this alter was a child. Clarification of this led to better understanding of the particular sexual predicaments in which this patient frequently found herself. Ultimately, the patient was able to extricate herself from an abusive sadomasochistic sexual relationship that strongly evoked this alter.
Along the same lines is this journal article, available as a free PDF:
Su Baker (1997) Dissociation Volume 10, No. 4, pp. 214-222, Dancing the dance with dissociatives: some thoughts on countertransference, projective identification and enactments in the treatment of dissociative disorders. Scholarsbank: download PDF
Abstract: Therapists working with dissociative patients, with their complex, overlapping transferences, frequently encounter countertransference conundrums. Further complications arise as the dissociative patient frequently uses the defense of projective identification, whereby the therapist is left "holding the bag," experiencing the patient's unwanted feelings or unacceptable impulses. Patient and therapist become the inevitable participants in transference enactment, each unwittingly playing a role written from the patient's past. However, projective identification and enactment may both be viewed as a powerful type of communication, allowing the therapist to understand the experience of the patient in a uniquely empathic way. By creatively welcoming inevitable enactment, the playing out of the patient's unconscious dynamics in the therapy, the therapist and patient can work through otherwise uninterpretable clinical material. This paper proposes that in the transpersonal field of therapy with dissociative patients, therapist and patient, "dancing together," can rework old patterns and arrive at new, deeper understanding and change. Case material is presented to illustrate this thesis.
Wikipedia: Projective identification