Jason Cole of Yahoo! Sports reports, "The basic agreement entails the Packers coming up with a list of teams willing to trade for the future Hall of Famer, then presenting him with the list to find out where Favre would prefer to play."
Cole hints that a deal may not happen any time in the immediate future. The Packers may, instead, choose to wait until there is an injury to a quarterback during training camp somewhere around the rest of the NFL.
It would be at that point that Favre's trade value may be at its highest. That type of situation would not be unlike the deal that sent Jason Taylor to the Washington Redskins when injuries necessitated a trade.