Ok, so I've been comparing the texture and bump maps that machf posted in my MinePass topic and I believe that the road on the table map shows a different section of road in the Pl area. Below is the bump map from the table map.

- PIslandModel00b8.bmp (65.05 KiB) Viewed 15456 times
we know from the walkthrough that the road seen in the retail portion can be considered accurate despite there being two sections that are impassible. But according to the table map that section is instead a serious of turns. Originally I thought this was the North road based on that it was important enough to have on the map, not to mention it's the only road there. But after noticing this I'm convinced that I was incorrect.

- _20170730_170525.JPG (44.67 KiB) Viewed 15456 times
In this close up we see that up till the turn the road matches the retail maps. But then it goes through a series of turns before going through the dot representing the dam. I recently noticed this is not on the retail section, on the retail map the road DOESN'T TOUCH the marker but goes around it. Not only that but it appears there's a black dot similar to the others in the center of the M like road. Going back to the bump map the area where the retail road runs seems unchanged, so it's possible this is a branch off of the North road. According to the walkthrough the only known ingen structures out here are the block house, radio tower (downed), and the fenced off dam area. The first two seem to remote to have a section notable section of road leading to them, granted though the exact location of the radio tower and wether or not it actually made into the level is unknown. But the fact of the matter is that the road leads to and through the dam marker. And now there's there's another dot which could only be the block house as it's the only object left.
Perhaps the building was more important than we know. All the walkthrough says is that it's "a small cement structure in the extreme north of the plains, contains some items which hint at some sort of story: a child's toy, some dishes, a weapon". The only internal description is from Ann about it being air-conditioned and guessing it was for storage. Maybe the unknown story was what made it important, otherwise we have another unknown about this level.