After two years on the Engineering Graduate Program, graduates have the opportunity to apply for specific roles within the company.
As a graduate you can only apply for non-graduate roles after two years, once that happens you are generally "snapped up" into a position which suits you (not necessarily the first one you apply for). After that you can get promotions once you have the necessary skills and experience.
Promotion will depend on experience, reputation and opportunities. There can be limited opportunity to move up if there is little movement from management positions.