It does not really matter which way you order the words of those two sentences. You can say "The rural poor are at the bottom of the heap" or "At the bottom of the heap are the rural poor." You can also say "At the schools are the students" or "The students are at the schools."
These two statements describe society, i.e. where you find certain categories of people. Students are found at the schools, the rural poor are at the bottom of the heap. In this case, "the bottom of the heap" is an idiom meaning the low end of society where people have little economic or political clout. The ones with the money are at the "top of the heap." They have power and political clout to change things. But the children, the students, are in the schools.
Here is a sample paragraph or little story I made up just now using the sentence structure you are asking about. I think it is quite effective in it's place.
In the schools are the students. In the vicarage is the vicar. In the
kitchens are the women. In the store is the merchant. And in the
precinct is the village constable. But the men, they are in their
fishing vessels on the sea.
So yes, in the appropriate situation we can use place-related nouns. Usually, though, it is for idiomatic or figurative speech. The students are not in school all the time and the rural poor are not literally under the bodies of the other community members like a pile-up of bodies in contact sports.
I think that little story describing the fishing village shows a natural application for that word ordering. In everyday conversation it hardly comes up.
Re-Ordering the Words & Clauses
Does it emphasize one specific part of the sentence?
No, as I stated at the beginning, one can order the words any way saying either:
- The rural poor are at the bottom of the heap.
- At the bottom of the heap are the rural poor.
What I did here was rearrange very specific clauses. When this sentence stands alone it does not matter which part comes first. In an on-going story, it might be important depending on what ideas had already been imparted to the listener. For example, a description of a community like the fishing village above might show the positions and accomplishments of the elite in the county, then add:
At the bottom of the heap are the rural poor.
"Heap" is figurative for "community" and the story had already introduced the concept of "community." Thus, it is stronger to put "rural poor" at the end. However, this is more a lesson in writing techniques; it does not change the meaning of the sentence.
Words Inside Clauses
What does change the meaning of the sentence is rearranging words inside the clauses. For example:
At the bottom of the heap are the poor rural people.
I had to add "people" because just saying "rural" is incomplete.
That sentence implies that not all rural people are poor, whereas "the rural poor" implies that rural dwellers are inherently poor.
Another rearrangement could be this:
The rural poor are in the heap at the bottom.
Again, I had to change a few words to make it grammatically correct; the goal is to rearrange "heap" and "bottom."
We now have more than one heap: one at the bottom and one or more that is not at the bottom.
NOTE: This applies to this particular sentence. I cannot speak for all sentences because I have not examined them. Thus, I am not sure if this really answers your question.