Get access to node titles and nid's only there are two content types on my site: Projects and Employees. Employees has a user reference field, Projects have several node reference fields to Employees (according to different project roles). I grant rights to users with Node access user reference and Node access node reference modules so they can view and edit only the nodes they are referenced to (either directly or indirectly). 
Certain referenced users (project managers) should be able to add other Employees in Project nodes but in the same time they must not see their personal data. Therefore they haven't got any referencable Employee nodes.
Would it be possible to grant access to the node titles (and nid's for referencing) only and hide other fields?
Yes you can, with  field_permissions module  you can set permissions according to the fields.