I think the ghost ship at the beginning has to do with the connection. When the race starts I think the game is making sure everyone is "synced" together connection wise because soon everyone turns solid.

It could also be why ships can sometimes turn to ghosts mid-race as the game might have a connection problem with the player or there could be some lag and the game is assuming where the ship would be.

I could be totally wrong and there may be some other reason for the ghosts.