To say the least, for reasons unknown, the Avalanche has acquired several former Canadiens players, and they will all be in uniform with the team soon.
Indeed, the defenseman has been called up by the team and will likely make his NHL debut for this season in the next game. He was playing in the American Hockey League after signing a contract with the team this summer.
It's worth noting that, apart from Lehkonen, the other three are players the Canadiens chose not to re-sign and who left as free agents. It's somewhat ironic that a rebuilding team didn't want them, while a contending team is playing them.