The use of the particle の with a list of objects (や or と)


I was reading the "A Dictionary of Basic Japanese Grammar" book on the
particles と and や to better understand how they differ and I ended up with a
question that I haven't been able to find the answer for; either in the book
or on the web.

My question is: can the の particle be used to indicate possession (or any of
the other uses it has in joining nouns) for multiple items when you have a
list using と or や? For instance, If I said:

> 学校の校長と看護婦が今来ている。  
>  The school principal and the nurse are coming now.

What I want to understand is if the sentence above indicates that the nurse in
question also works at the school, or if it gives no indication of that, or if
it is ambiguous. Is there some other construction to indicate explicitly that
both the principal and the nurse are from the "school"? What about the other
side of the particle? Would this be correct:

> 私と弟の文書はかばんにあった？  
>  My brother's documents and mine were in the bag.

Or should I write this differently to get this meaning? Also, are the rules
for using や to make an in-exhaustive list any different?




> 学校の校長と看護婦が今来ている。  
>  Only two people are coming (Other guests may not come).  
>  学校の校長や看護婦が今来ている。  
>  School principals and nurses are also coming now. (Others may come)

But above sentences do not show any other information. But I can guess 「来ている
coming」 is used for guests. Or they do not have any plan to go there (may be a
holiday or day-off), students found them at the school unexpectedly.

You can say for workers at this school. 「いる exist」 or 「戻ってきている return」can be
used.

