As far as I know there isn't a plug-in for AC12 yet. We are still using AC10 on a project because we only have the nwc-export plug-in for that version. On the NavisWorks website (Autodesk these days) they mention supporting AC11, but I haven't tried it.
Architect AIA RIBA SAR/MSA, Graphisoft Registered Consultant
AC19 SWE 7006
AC20 SWE 4012