There is not a rule that precludes this, but it is discouraged as one of the purposes of this event is to encourage the learning of new repertoire.
All works at this event are accompanied by piano. If you have a score that is written for voice and piano, or harpsichord, or organ, or similar, that’s fine. If a piece has an obbligato for flute or clarinet, or any other instrument, that doesn’t ban it from the Auditions; just don’t expect to hear that part (and don’t bring a flutist or any other instrumentalist other than a pianist.) If you have something out of the ordinary that you’d like to present at the Auditions, you must get permission from the Repertoire Consultant to do so.
While there is no rule against borrowing a score or sharing a score with another singer during the Auditions, problems can arise if you arrive and find out your teacher forgot the book, or brought the wrong key, you’re singing at the same time as your friend, or you’re singing in separate locations. Owning and bringing your own original scores will eliminate these problems, and help you build your own singing library. For this event, you only need one original score for each song you perform.