This is all Autodesks grand plan to "mess with Sasquatch" - they don't make it easy to work with their data and make it difficult for everyone to use unless you use AutoDesk products - the civil data and xref data is likely not in the file you have - and it may be hard to get at.
Good to see you all tag teaming this to solve a "data transfer problem" - I had hoped that after 30+ years in this business we would be beyond reading and writing files to make projects work
Sorry this is such a pain we are trying to help here but every year they introduce more and more complexity into this scenario- you are better off using non Autodesk Standards if you want interoperability
Alan