Kotaku reports Canessa will be joining the teams responsible for Diablo and World of Warcraft. However they don't actually cite a source and Blizzard apparently didn't respond for a comment 'immediately', which is quite an odd way to phrase it.
Update: Blizzard spokesperson Shon Damron got back to us confirming that Greg Canessa has indeed been hired by the company:
"Yes, we can confirm that Greg Canessa has taken a position at Blizzard Entertainment as project director for Battle.net. He will report to our vice president of online technologies and work closely with the executive team to help fine-tune the next version of Battle.net, currently in development."