Отсутствует связь между кастомными таблицами.

Не удалось получить список районов

$out = '';
            $towns = $modx->getCollection('Towns');
            if (!$towns) {
                $hook->addError('areas','Не удалось получить список городов');
                return false;
            }
            foreach($towns as $town){
                $areas = $town->getMany('Areas');
                if (!$areas) {
                    $hook->addError('areas','Не удалось получить список районов');
                    return false;
                }
                foreach($areas as $area){
                    $out .= '<option value="">'.$town->get('title').' - </option>' ;  
                }
            }
            $hook->setValue('areas',$out);

<?xml version="1.0" encoding="UTF-8"?>
<model package="geolocation" baseClass="xPDOObject" platform="mysql" defaultEngine="MyISAM" version="1.1">
	<object class="Areas" table="areas" extends="xPDOSimpleObject">
		<field key="town_fk" dbtype="int" precision="10" attributes="unsigned" phptype="integer" null="false" />
		<field key="title" dbtype="varchar" precision="255" phptype="string" null="false" />
		<field key="is_default" dbtype="enum" precision="'1','0'" phptype="string" null="false" default="0" />
		<aggregate alias="Towns" class="Towns" local="town_fk" foreign="id" cardinality="one" owner="foreign" />
		<composite alias="Streets" class="Streets" local="id" foreign="area_fk" cardinality="many" owner="local" />
	</object>
	<object class="Regions" table="regions" extends="xPDOSimpleObject">
		<field key="title" dbtype="varchar" precision="255" phptype="string" null="false" />
		<composite alias="Towns" class="Towns" local="id" foreign="region_fk" cardinality="many" owner="local" />
	</object>
	<object class="Streets" table="streets" extends="xPDOSimpleObject">
		<field key="area_fk" dbtype="int" precision="11" phptype="integer" null="false" />
		<field key="title" dbtype="varchar" precision="255" phptype="string" null="false" />
		<field key="adress" dbtype="varchar" precision="255" phptype="string" null="false" />
		<field key="phonenumber" dbtype="char" precision="12" phptype="string" null="false" />
		<field key="is_default" dbtype="enum" precision="'1','0'" phptype="string" null="false" default="0" />
		<field key="in_map" dbtype="text" phptype="string" null="false" />
		<aggregate alias="Areas" class="Areas" local="area_fk" foreign="id" cardinality="one" owner="foreign" />
	</object>
	<object class="Towns" table="towns" extends="xPDOSimpleObject">
		<field key="title" dbtype="char" precision="20" phptype="string" null="false" />
		<field key="region_fk" dbtype="int" precision="10" attributes="unsigned" phptype="integer" null="false" />
		<composite alias="Areas" class="Areas" local="id" foreign="town_fk" cardinality="many" owner="local" />
		<aggregate alias="Regions" class="Regions" local="region_fk" foreign="id" cardinality="one" owner="foreign" />
	</object>
</model>

$towns = $modx->getCollection('Towns');
            if (!$towns) {
                $hook->addError('areas','Не удалось получить список городов');
                return false;
            }
            foreach($towns as $town){
                $areas = $town->getMany('Areas');
                if (!$areas) {
                    $hook->addError('areas','Не удалось получить список районов');
                }
                foreach($areas as $area){
                    $out .= '<option value="">'.$town->get('title').' - '.$area->get('title').'</option>' ;  
                }
            }
            $hook->setValue('areas',$out);

return false;