Can applicants who aren't students yet apply through ProEMS?
Yes. With outside admissions switched on, your ProEMS sign-in page shows an Enquiry button anyone can use, and with enrolment switched on it also shows Apply for Admission.
Enquiries land in Pre-Admission, where you turn them into candidates, email the admission form link and confirm or cancel each application. Applicants can reopen their form with their reference number and email. These are Platinum features; the admissions page has the full flow.