EY does not participate in any TTP, thus there is no place to add one's KTN and, even if there were, it would do no good. Your friend will not receive Pre-Check treatment while flying EY other that through some random or other managed inclusion having nothing to do with the friend's TTP participation.

Better for your friend to send a note to EY encouraging it to participate in Pre-Check so that its eligible may receive the benefit of the program should they choose to join it.