I think closed caption data for SD content is visible on line 21, and it can be seen in a broadcast monitor using underscan. I can re-export the video, or even delete the track in QuickTime pro and re-save the QuickTime. That will get rid of the empty track. However, I'm digitizing content for archival purposes, and I'd prefer not to add another step (and one that I might forget to perform) to an already cumbersome workflow.
I think it's strange that FCP would automatically create an EIA-608 cc track. I wonder if anyone else has experienced this, or knows how I can keep it from happening?