The trouble of this isn't so much of the service but the goods that are required to receive such service. In the 90's I could easily find analog cable boxes in retail stores...there was even a product called a "rabbit" that would mimic a box to another tv. Most TV's even today have tuners so you don't need a box (except naturally for scrambled channels...hbo's, ppv's, sporting events etc)
Everyone knows that digital cable is better in terms of visual and numbers of stations...ultimatly analog will die out. Having said that it seems that cable co's don't want you to have your own digital box for a few reasons
1) they fear hacking to watch pay material (frankly I think this is BS since anyone watching it knows it's a 2way service...the cable co won't send a signal out if it doesn't receive one back...thus it knows who has what)
2) they want to do more targeted advertising. Everything you watch on digital cable (ppv's, shows, commericals, on demand) can easily be given back in demographics is is gold to advertisers...
3) they can make far more in renting something out rather than selling it. Even if a box cost $300 they could rent it out for say $12 a month for a decade or so to a consumer.
The way the courts are ruling is slowing going to develop into a private market. By making it open up just a bit it can help consumers to a point. Let's say someone owns more than one house...now because the cable co's can vary from town to town why should someone rent two boxes if they only need one? Why should one box not work with another provider if the customer is obviously paying for service?