Usually teams don't allow other teams a window to speak to their pending free agents. San Jose did with Clowe. I don't remember it happening in the NHL before that.
It seems to happen more often in football. I like it. It's empowering to the player, and its beneficial to both sides. Go see what you can get, and come back and let us know.
acouple things can happen
1) he decides the options aren't to his liking, either money or term, or teams willing to meet the money/term. Decides for what is being offered he prefers to make the best deal with current team.
2) he finds a match with another team, and that team tries to hammer a deal with the rangers and the player has his deal, his location, and his old team gets much more value then as a rental.
3) he finds a match with another team, but the rangers can't agree on compensation. Agent tries to find another location which is a match, and they try to repeat option (2).
4) he find a match with another team, but the rangers can't agree on compensation with any possible suitor. Callahan decides I won't resign with any team until July 1st. The Rangers then know what Callahan's plan is and decide whether they trade him as rental or keep him for playoffs and let him walk.
I think this is a very proactive move. Also I think this is a negotiating tactic. To create stir, to create the dynamics, both logistically and emotionally for Callahan to have to deal with, am I really going to leave? This puts both sides on notice, and forces them to face these decisions now, and everything that comes with it. The feelings, the reality of it, the fall out. It's like getting a glimpse into the future, but being able to decide before it happens swiftly, what do we really want.