This transport is for the Rebel Alliance in the Fighter Squadron game mode. If one appears in game, it will have 30 seconds to be escorted before jumping into hyperspace. If the Empire manages to destroy the transport before it can escape, they will be rewarded with 20 points.
The transport also reappears as a prop in Supremacy, which is used when Rebels are pushed towards their legs.
The transport plays a major role in Walker Assault, which the Rebels need to defeat the AT-ATs in order for the transport to leave safely. If the Rebels fail, a cutscene will play showing the Walker firing at the transport while it takes off, exploding in the process.
The transport also appears in Extraction, once the Rebels reach the last checkpoint, the transport hovers down, ready to pick up the cargo and crew. If the Rebels succeed, the transport will hover above and take off, but if they fail, the transport doesn't move.
The transport also appears in Sabotage, where the rebels must defend the Extraction Point, otherwise they cannot escape the Imperials.