What I personally experienced in therapy was not so much attachment to the T, but an addictive-type preoccupation with the whole therapy thing, the self examination, trying to understand the whole process. As far as interpersonal domain, I felt a strong connection with my last T, which felt pleasant and it definitely increased my motivation to go to sessions. I am not sure about the therapeutic benefit of it though - for me it felt very similar to what I often experience with friends or work colleagues that I like, not unique or special at all. I never worked on anything related to attachment in therapy though.