The attachment of an area to a city is done by saving the area to city in WordPress. The correlation is with code and you would need to follow these technical instructions to get the exact structure of the database. We use standard wordpress database structure but to see the exact layout, please consider below instruction:
in property.php is saved with
update_option( "taxonomy_$t_id", $term_meta );
is taxonomy id.
you should print_r get_option( "taxonomy_$t_id"); to see how data is stored
And then create the xml/import based on the database structure and the cities/areas you need to import.