There are several different Turnitin products and licences. The University of Oxford has a licence for Turnitin (Academic), which allows the screening of work of registered Oxford students, submitted in terms of curriculum requirements. There is a separate product, Turnitin (Admissions), which allows screening of work submitted by applicants to the University (prospective students).
Graduate Admissions is currently running a small pilot project using Turnitin for Admissions. The Blavatnik School of Government, the Saiid Business School and the Department of Education are currently using Turnitin for this purpose. Read the case study about it, or contact Richard Turner for more information.