According to his LinkedIn profile, Greg Spence is now associate producer of HBO‘s Game of Thrones. According to Wikipedia, an associate producer, “usually acts as a representative of the Producer, who may share financial, creative, or administrative responsibilities, delegated from that producer.”
Spence has a significant amount of history with HBO in similar roles, having been associate producer on their award-winning miniseries, John Adams and Generation Kill, and the recent film Temple Grandin. He also appears to have extensive experience in post-production management, suggesting one of his roles will be to oversee post-production of episodes.