There are lots of seemingly "backwards" areas like that - Where you would expect high-speed availability, there is nothing, and you can get fiber to the house out in the middle of nowhere.
It apparently has a lot to do with how well the local phone company has been dealing with steadily (and unsteadily) increasing demand over the years. With the relatively sudden (but still predicted) explosion in broadband, a lot of providers in urbanized areas were caught completely off-guard, because they hadn't paid any attention to upcoming technology and spent all of their resources on the old, antiquated systems that had been sufficient for so long. Out in rural areas however, with relatively little in the way of "plant" facilities to keep running, a lot of small-time telcos found themselves able to provide high-speed access to their entire user base just by using some of their previously-excess capacity and upgrading a few of the outlying runs.
When I was living in Dallas and plugging along with a fidgety dial-up connection that rarely topped out 28K, the little crap-town I had lived in in Arizona was delivering partial T-1 to the doorstep, just because they could.