There are clear differences between depersonalization and the Buddhist concept of non-self. For one, in depersonalization, there is no sense of choice about the experience. People don’t like depersonalization, but don’t know how to avoid it. Non-self, on the other hand, is an experience that one chooses to develop. Depersonalization is associated with suffering, often greater anxiety and depression, while non-self is associated with to a sense of well-being independent of external circumstances. Depersonalization is typically experienced as an affliction or illness, while non-self is willingly sought out. Depersonalization is also associated with cognitive impairment, particularly in attention and working memory, while non-self, developed through meditation, is known to improve attention. Ultimately, depersonalization makes a person less functional in life, while there is every indication that mindfulness makes people more functional.
But aside from speculation, a study has been done that shows an opposite relationship between mindfulness and depersonalization:
Michal, M., Beutel, M. Jordan, J. Zimmerman, M. , Wolters, S., & Heidenreich, T. (2007). Depersonalization, mindfulness, and childhood trauma. Journal of Nervous & Mental Disease, 195(8), 693-696.
Abstract: "Depersonalization (DP), i.e., feelings of being detached from one's own mental processes or body, can be considered as a form of mental escape from the full experience of reality. This mental escape is thought to be etiologically linked with maltreatment during childhood. The detached state of consciousness in DP contrasts with certain aspects of mindfulness, a state of consciousness characterized by being in touch with the present moment. Against this background, the present article investigates potential connections between DP severity, mindfulness, and childhood trauma in a mixed sample of nonpatients and chronic nonmalignant pain patients. We found a strong inverse correlation between DP severity and mindfulness in both samples, which persisted after partialing out general psychological distress. In the nonpatient sample, we additionally found significant correlations between emotional maltreatment on the one hand and DP severity (positive) and mindfulness (negative) on the other. We conclude that the results first argue for an antithetical relationship between DP and certain aspects of mindfulness and thus encourage future studies on mindfulness-based interventions for DP and second throw light on potential developmental factors contributing to mindfulness."