Problem - Attach a Shapefile as a Reference File in OpenCities Map and the result is that you cannot see the features, and the MicroStation Message Center reports "No Elements Found" when you use the Fit View command.

Solution - Verify that the .prj file is valid, and if it is invalid, move or rename the .prj file so that it is not scanned or read during the attachment process.

Shapefile spatial reference information files, the .prj file, may become corrupt for whatever reason.  When this happens the Shapefile will not behave properly whether it's imported, referenced, or read into the software in some other manner.  Here is a look at a .prj file that is invalid, notice there are opening brackets with no closing bracket for the value.  There appears to be some additional brackets where none are needed:

Bentley Map V8i (SELECTseries) produced some additional information that can help troubleshoot the problem: An information dialog box is displayed upon attaching the Reference, and the MicroStation Message Center adds supporting details:

  

This issue can also occur when the Name of the Active Coordinate System in the DGN File matches the same name as the Library Coordinate System, yet the units & values are different.

Try these suggestions if you have issues attaching Shapefiles as a Reference in MicroStation or OpenCities Map, they may be a quick resolution to the problem.