I have COX Cable for Internet only. No additional fees, in fact no franchise fees or other quasi-taxes that they would otherwise charge for cable and/or telco service. I have a service called "Internet Starter". They do not advertise it on their web page because they want everyone to pay for additional bandwidth. If all you do is surf the net and can live with a DSL quality speed you can get the service for $28.99/mo.
Many cable companies sell internet without TV. There is typically an additional fee, since they tend to build the cable installation/maintenance cost into the TV part.
I think the simplest installation would just keep it all separate. ie: if they don't share any wiring, then there's not much to mess up or any fingers to point. eg: the internet can connect to a router, and never see any Dish or interior TV wiring.
In case you were wondering, my telco service stinks as far as getting broadband (even my dial up speeds were terrible). I'm too far from the CO to get anything above basic DSL which would be $20/mo. The Telco (at&t) wanted $200 to install since I don't directly subscribe to their POTS service. I said no thank you and got COX instead.