Pre-order incentives hardly ever stay exclusive anymore, and Watch Dogs 2 is yet another example of why waiting to pounce has its advantages. Not only will you net a lower price, but chances are whatever pre-order incentives are offered usually end up in everyone else's hands eventually. In this case, it is the ScoutXpedition mission, which was free to PS4 players who pre-ordered the game. Now, it is open to all PS4 players who own Watch Dogs 2.
Here's the official description of the mission per its PSN Store page:
"Cruise through the streets of San Francisco as you take a movie location scout to some of the city’s most iconic locations in this bonus mission."
You can grab the mission starting right now directly from PSN, but (and I shouldn't have to say this but…) you have to have a copy of Watch Dogs 2 to play the ScoutXpedition mission (duh).
Source: [Power Up Gaming UK]