It keep anyone else in the division from getting him. That by itself is a win. IMO it's a push as far as making the team better. +/- 3 games, tops.
And Bill, he's not on the Red Sox either.
The fact that RH is 2 years older than Lee might bother me if I were a Phils fan. I assume the Phils think they have a better chance of signing RH to a long term deal than CL.
CL is a free agent next year. He can take Pettitte's place in the rotation.