as for most commercial sports venues in Australia such as AFL, Australian Tennis Open, etc, the average punter attending can take photos for non-commercial usage but they generally will be denied entry to the venue if their lens is more than 200mm in focal length.
the reason for this is that the sports companies such as AFL seek to control all commercial usage of sports images of their events as they believe they hold the commercial copyright to any images taken at the venues
accredited photographers CAN gain special access on the ground and use whatever lens size they wish, BUT although they can use the images for news purposes, the images cannot be exploited for commercial usage.
in addition to such accredited photographers, AFL Media employ a number of photographers to create the AFL's own content such as for merchandising, clubs, websites, etc.