The MicroStationAPI and the DgnPlatformNet have a CreateSharedCellElement() method (as of Update 10). It creates an instance, or placement, of a shared cell element in a DGN model.
CreateSharedCellElement()
Why isn't there a C++ .NET similar method for creating instances of normal cells? Consider these existing methods:
CreateCellElement2
mdlCell_getElmDscr