Is you Google rusted brake lines you will find out that it happens every where and not just on your Georgetown. Not sure what you want to hear from us. If the line failed you still would still have brakes on the other axles as they have dual lines and not all the brakes are effected.
Yours is the first I have ever read here and I have been on this forum for many years.
Have you contacted Ford yet? Have they offered to replace the brake line?
Please update us on what you have done so far.
Try this link and see all the pictures of rusted brake lines.