Hi Gerald,
If Step format is available for exporting you should use that format, Even most third party CAD to CAD or CAD to Viewable (ie JT) translators use STEP or a middle format in the background.
As for IsoDraw to have a direct NX data interchange is highly unlikely unless a third party developed it and most likely it would do a STEP translation in the background...
Tony
Arbortext IsoDraw supports CreoView Adapters which enable you to import "JT" files fron NX and Teamcenter. The CreoView Adapters can be purchased separatey.