You have to bring it into a drawing first, then copy paste it to a CATPart.
or
Bring it into the drawing file, then save it out as a .ig2, this is a 2d iges file.
In windows change the extension to .igs
This will come in as a CATPart file.
just out of curiosity, is there any other way to import these 2D model into 3D? changing the file name to fool catia seems kinda silly.. but it works...