Left For Dead, Payday: The Heist crossover revealed

Swedish developer Overkill Software has revealed that it is working with Valve on an "in-depth collaboration".
In a post on the studio's website Ulf Andersson, game director on multiplayer FPS Payday: The Heist, writes: "We are excited to be able to confirm that an in-depth collaboration between Overkill and Valve is currently in production.
"We are working on a very cool blend of Payday and Left 4 Dead. I am sure it is so exciting that it will have some players check into the hospital before we are done."
The announcement follows the release earlier this month of a patch for Payday: The Heist which added several hints to a Left 4 Deadlink - such as the below image showing some L4D health packs.
http://www.edge-online.com/news/left...sover-revealed