Kentucky is full of mountain roads with questionable maintenance and build quality which are used by coal and mining trucks all the time. They are basically one lane roads too.
As long as the "road" is kind of flat and made of something slightly more sturdy than sand, these trucks can get through.
I don't think the Kentucky coal mining scene is the ideal comparison here or what we should hold up as the aspirational standard for new initiatives. Especially when you say the roads are poorly maintained, and especially when the Maine road in question isn't just some mountain road, it's the main highway through a significant portion of Maine, and a secondary highway (parallel to I 95) through other parts. What you describe on Kentucky sounds minimally adequate for its own needs and not at all comparable to this situation.
As long as the "road" is kind of flat and made of something slightly more sturdy than sand, these trucks can get through.