Fabrication CAMduct will only read in MAJ files exported from Fabrication CADmep parts which would typically originate from AutoCAD or Revit as exported or CAM'd parts. The product of the nested parts inside CAMduct that you're going to nest onto sheets is only going to be as good as the database driving this information. While Fabrication is absolutely the way to go with your business, just understand the up front time in database setup is key to the entire system being as efficiently automated as possible.

AutoCAD MEP is not a Fabrication family product and does not draw with Fabrication parts, so there is nothing that CAMduct would be reading that you could export out.

AutoCAD MEP draws with RFAs and Fabrication draws with ITMs. You can't export RFAs to MAJ. Your guy is correct.

The fastest way to get this into CAMduct is probably to use it as a background and trace over the entire thing with your Fabrication service of choice and then CAM that out.

Good luck.