esass13,
Is this a design-bid-build?
Why do you care if he tears up the curb and replaces it?
With standard construction, there is also a good chance of undermining the pavement, so that could have to be replaced.
In any case, there is certainly a much higher cost associated with installing water mains that close to a curb.
If it were a small piece, maybe you could try to do it, but for a long run, it's probably better to just tear up the curb.
Also, if there is curb and asphalt pavement, the excavator will tear up the pavement.
Good practice would be to keep the water line a few feet off the curb, but I assume you have some reason that you can't do it that way.