An interesting functionality extending the standard AutoCAD linetype mechanism is hidden (almost unnoticed) in the DGN Import command. This functionality is available since AutoCAD Civil 3D 2011, plus in all versions of the AutoCAD 2012 family. The DGN import allows to convert and use special linetypes which were otherwise unreachable in AutoCAD.
Microstation defines these complex linetypes in the .RSC files. And just these files are interpreted by AutoCAD during the DGN import -- the linetypes used in the DGN drawing are converted into special, extended AutoCAD linetype definitions. With these enhanced definitions you can use exotic linetypes which were not available so far in AutoCAD. Examples:
Lines and polylines with these linetypes behave like standard DWG entities but their extended linetype definitions do not translate back to older versions of AutoCAD, nor can be exported to .LIN files with our LinOut utility.
More information in the CAD Forum tip Unusual AutoCAD linetypes from RSC.