Each applicant receives multiple interviews and I can perform one of these as a PhD student, and have received the same training any faculty member would have.

The interview process is relatively standardized, and if my results were to differ starkly from what more experienced interviewers do they would be disregarded, and the director of studies for that college would simply not invite me back to help.

I would add that asking PhD students to do this is not the worst thing because via supervisions and other teaching efforts, we have a good picture of what undergrads here need to be able to do. An interview is a like a short supervision.

Thanks - that actually sounds fairly sensible.