Sometimes it's useful to add bars and tone in a tapeless workflow. I regularly add a little at the beginning of files that go out-of-house, since I know that the files may get transcoded at another facility, and the bars are useful in determining if there have been any transcoding issues (gamma shifts, level/colour distortions, etc.)
Edit in FCPX make everything look as good as possible. Then put T&B on the front of the video and export. Then launch FCP7 or M100 or any NLE w/output to AJA or whatever card. Check the Bars on external scopes, adjust as necessary and then export to tape.
This is how I am planning to use FCPX on a couple new projects.
I created a generator in Motion by modifying a generator from FCPX there, replacing media with a set of bars from a BMP. I now have a generator called Color Bars in my generators tab. It is easy to import tone.
Since Motion projects including Generators don't include audio tracks - why not output Bars and Tone as a QT movie from FCP 7? Then import this movie into your Event(s). What's nice about this is it's a self contained movie that includes the Tone audio.
I have a ten second clip(s) if you want it ... both 1080p HD and NTSC DV