Finding corresponding category in different subtrees of a category group
I would just split that category group, if possible, and offer one group for the region and one for the “A1” type of categories.

If this is out of question, you need to find a way to link your categories. Give them the same slug or use another field to make the connection (e.g. a Categories field) and use the corresponding criteria param to filter for the entry in the new locale.

$currentLocaleCategory = $entry-&gt;myCategoriesField-&gt;last();

if ($currentLocaleCategory) {
    $criteria = craft()-&gt;elements-&gt;getCriteria(ElementType::Category);
    $criteria-&gt;locale = $locale;
    $criteria-&gt;descendantOf = $descendantOfParam;
    $criteria-&gt;slug = $currentLocaleCategory-&gt;slug;

    $newLocaleCategory = $criteria-&gt;first();
}