What I do in this cases is to make two associations. Since cake allow to customize relations, you can have two relations to the same model with different names.
public $belongsTo = array(
'ResponsibleEmployee' => array(
'className' => 'HrEmployee',
'foreignKey' => 'responsible_person',
'fields' => 'HrEmployee.employeename',
),
'AttendingEmployee' => array(
'className' => 'HrEmployee',
'foreignKey' => 'person_attending',
'fields' => 'HrEmployee.employeename',
)
);
Change the names to adjust your needs. Now, if your model is set as containable and you retrieve the Project model with those models in it, you'll get something like
array('Project' => array(/*data project*/),
'ResponsibleEmployee' => array(/*name*/),
'AttendingEmployee' => array(/*name*/)
)
(or another variation of that array depending on how the query was made).