I'd be surprised if they have to tear up the walkway. Or really anything. The line they're going to run is very small so they shouldn't have to do a whole lot and it can be ran under the walkway without a lot of hassle. You're house is still probably on some list saying you have Comcast equipment like an ONT in it, even though you're not a customer.

I'd be annoyed too, but it's likely just a case of poorly updated databases. There's probably still Comcast service off the main line at the street so they think it has to be updated with everything else.