They buy it from Tribune Media Services. They're one of the standard suppliers of such data.

And if I go to zap2it.com (a Tribune site I think with data equivalen to what Tivo gets) and plug in a Fairbanks zip code, I get to types of GCI cable service and what looks like 3 satellite lineups.

I haven't bothered to do it yet, but I gather that networked-enabled Tivos scrape lineup data from some zap2it/Tribune system. I bought a lifetime subscription, but my dialup success rate is not so hot so I may do this just for reliability's sake.