Also post links to studies if you find them. All I found was these three about shadowrun.
http://topnews.ae/content/23090-microsoft-dropped-cross-platform-gaming-project-reports
http://www.engadget.com/2010/07/25/hps-gaming-guy-says-microsoft-killed-cross-platform-play-due-to/
http://www.gameranx.com/updates/id/713/article/microsoft-aborted-cross-platform-online-gaming-project/
shield.