There is involvement at my current site across the board. The official selection committee includes psychologists on the training committee and current postdocs. They conduct the individual, evaluative interviews and attend the ranking meetings. The current interns hold small Q&A sessions for interviewees. Our part is not officially "evaluative" as in we do not fill out a form ranking each person, but the TD came to us after each session to get our impressions of each person. So now you know the players (haha).
On to the process (as best I understand and can articulate it). It starts with the review of AAPIs using an evaluation form that is a likert scale where the applicant is ranked on many domains (breadth of clinical experiences, assessment skills, research, essays, etc.) So they are pre-ranked before interviews based just on their written materials. There is a second evaluation form that is filled out after each individual interview. It is also a likert scale across domains (attire, confidence, articulation, perceived level of site interest, fit, etc.) with places for specific comments. All of this information is put together by the TD and assistant TD in an excel spreadsheet that is distributed to the selection committee to review for a few days before the official meeting where the final rank list is put together. Apparently that meeting centers around a slide show where each person is discussed one-by-one. Their ratings are reviewed and the TD includes verbatim notes/comments from interviewers and interns to include in the presentation. They start by determining who to simply cut and not rank at all and then they squabble over the order of how to rank everyone else. I have heard (unofficially) the meanest (as in the least easily impressed) and loudest voices win.