I think to be promoted you really have to be good at what you do, show an interest in learning and also have a good work ethic and 'can-do' attitude. Traits like this will be recognized and can set you up for success.
Strong career prospects however lack of clarity surrounding hiring period post graduate program.
Rolling off the graduate program includes a guaranteed role. However, depending on the team, promotion possibilities vary. May be as simple as being a high-performer or having to look for another role in order to gain a promotion.