You need to buy it when it's released through a subscription or single purchase, or acquire it through other means, you dirty pirate.
I just wonder, what happened to the other guys in the van, aside from the driver and Ned Luke? What if we actually play as more than 3 characters during the bank robbery, but they're killed as part of the story, and we end up with those 3 protagonists for the rest of the game? I'm betting that the bank robbery is one of the first missions of the game, and that acts as a set-up for the rest of the story.