Sure you can.
The inherent costs to provide services is similar, but Comcast can amortize costs over a larger customer base. If Comcast is at all competent (a huge if!) then they should have overall lower costs, even taking (probably reduced) profits into account.
Customer service needs to be provided, a mailing center to send out hardware, a billing system, technicians and installers need to be trained and dispatched, payroll for all said employees, and all the other costs of running a business that should, in theory, scale to Comcast's advantage.
And of course Comcast can offer quicker upgrades in service. By bringing resources to bear, they should be able to iterate on technology faster than a municipal provider can.
Comcast also has the advantages of bundling services, another way to recoup costs and compete vs the municipal provided service.
A well ran national company with should be able to put up one heck of a good free market fight going up against a municipality. The real question becomes, is Comcast able to put up that fight?
