This seems less like an anniversary celebration DLC, and more like one day about a week ago, someone over at VSTEP headquarters decided to check their calender for the first time in 3 months, and yelled out, "Oh, Jeez, guys! The two year anniversary is coming up next week, and we've got nothing!"
At which point someone poked his head out from his cubicle and suggested, "Hey, I keep on seeing a customs boat sailing around in the harbor that kinda-but-not-really looks like our P6! Maybe we can contact them? If we get their permission, it wouldn't take very long to retexture the P6 to look like it! It's like what we let people do in Ship Simulator 2008!"
"Great! You get on that!"
One agreement/sellout later, they got the permission they needed, and one few-hour photoshop job and several-hour mission editor (Seriously, that thing is INCREDIBLY user-unfriendly) session later, our "brand new" DLC was born!