Это один из способов, возможно, есть несколько других.
$result = $this->User->Vehicle->find('all', array(
'recursive' => -1,
'conditions' => array('Ownership.user_id' => 66),
'fields' => array('Vehicle.*','Ownership.*'),
'joins' => array(
array(
'table' => 'users_vehicles',
'alias' => 'Ownership',
'type' => 'LEFT',
'foreignKey' => false,
'conditions'=> 'Vehicle.id = Ownership.vehicle_id'
)
)
));
$list = Set::combine($result,'{n}.Vehicle.id','{n}.Vehicle.name');