IGN has posted a Q&A with Gareth Reeder, Producer of NBA Live 09.
IGN: "How are hot and cold streaks decided?"
Gareth Reeder: "There are actually two different streak values we look at from Synergy Sports Technology. The first is your traditional "shot" streak; if a player shot better than he usually does during that game, then he will be hot in the game. This is most determined by the player's shooting percentage, but also takes into account his position and other factors."
Update: We've just uploaded the NBA Rewind Producer tutorial video.