However, Civil 3D objects (Surfaces, Alignments, Profiles, Pipe Networks) have a unique relationship with XREFs that standard AutoCAD objects do not.
Yes. You can extract data from an XREF using the _EXTRACTXREFDATA command (formerly _EXTRACTXFDATA ). This allows you to select contours or 3D faces inside an XREF and convert them into a native Civil 3D Tin Surface. However, the surface will not update dynamically if the XREF changes—you must re-extract. civil 3d xref