reply to ComCost
Re: Long run, long shot? If they are telling you that your address is serviceable, set up an install, with the understanding that the installer shows up and says you aren't. At that point, the installer should be able to give you more information about who to talk to about making your home serviceable, and/or will submit the information themselves.
If your sister is going to also sign up, who lives between you and the existing plant, it may be easier to get this done, as they will have two people paying, meaning the cost per customer to install is less than if just you were to be installed. I deal with these types of issues a couple of times per year.
Your other option, is calling the sales person that they gave you, and talking to that person. Explain the distance, and if they want the sale, or better, the money for the sale, he/she will put you in contact with the correct person to possibly get you installed.