The Thrashers won't be participating in this year's Traverse City prospect tournament, unfortunately (despite what the Blues' non-updated/copied from last year press release says), but the Blues'll have to take on the Bolts, Stars, and Wings in the first four days of the tournament as part of the Howe Division. The Gretzky Division consists of the Jackets, Rangers, Canes, and Wild for this season's tournament.
The tourney's always seen as a chance to evaluate the organizations' young prospects in a setting that gives a good idea as to what they can really do. Prospect camp is useful for evaluating the talents of the local NHL team's prospects in a small setting, and scrimmage games help aid a person in seeing how they exactly can function in a competitive setting. Of course, an outcome to the competition's a productive way to encourage said competition - and other than the "yaaay, we won the scrimmage!" chat, there's not much in the way of a reward for winning at camp.
Traverse City's a round-robin tournament that pits players against other prospects who they may or may not know. It diminishes the odds that they'll be playing against the predictable styles of their friends and places them in a competitive setting significantly closer to what they'll be exposed to in NHL play. Not only will this give the scouts and player development staff from the participating teams a chance to examine the kids in a realistic setting, it's a great chance for fans of other teams to see what the participating squads have in the pipeline. In theory. The NHL Network's not airing it this year for some reason, so don't turn it on expecting to get a chance to see Ian Cole and Alex Pieterangelo scoot around the ice. You'll have to follow it day by day on the Blues' website - right now all that's up are the rosters, which look sharp and extremely not-European at all. Look for the entirely North American team to put up a good showing this season. The defensive corps themselves should help the team win a few games.