You can get/set VolumeManipulator matrix using setLookAt and getLookAt, this will give you position and orientation informations with Mat4x4.getLookAt* methods. The setPosition method was in fact an old method which may be removed.
VolumeManipulator camera implementation is intented for manipulation volume (model, ....), you may which to use a different/your own implementation if you need different behavior.
The Vec3 getter parameters are destination vector for storing result.
All the math api is design this way (for performance reasons): it's up to you to allocate (or reuse) destination object.