If the tone & bars clip was generated as 4:3 then it'll probably appear as 4:3 in iMovie. Even if it was generated as 16:9 in FCP (Final Cut Pro) then it may appear as 4:3 in iMovie if (a) FCP hasn't set the widescreen 'flag' (setting) in the clip and Saved it as widescreen, or (b) if you imported it into an iMovie project which had a 4:3 clip at its start.
If you have QuickTime Pro (..you can download a $29.99 'key'
from here* which turns QT into QT Pro..) you can easily resize any QT .mov clip to any dimensions you want ..e.g; to 16:9 from 4:3:
..you simply type new pixel numbers into the relevant boxes. (Bob Whatsisname used to have a tutorial on this; the elements are still the same, but in newer versions of QuickTime some of the menu items have been moved to different positions from
those in his video here.)
..Or see the QT Pro Tutorials
here.
If you have iMovie '08, and if your first clip in an iM08 project is a DV
Widescreen clip, then when you drag in a 4:3 clip - such as your bars and tone - that'll be automatically cropped to 16:9. Then just Save it and Export it as 16:9 to use in iMHD6.
For example, here's a 4:3 clip:
..dropped into an iM08 project which has as its first clip a 16:9 clip, and is set up as a 16:9 project, whereupon the 4:3 clip above is immediately cropped to 16:9..
..Simplest way of doing it, if you have iM08.
It's a while since I've used FCP HD (..iMovie can usually do everything which I want..) but I'll see if I have a few moments free today to do it for you and post the results ..or - you'll probably get a quicker response! - just post your question (..about ensuring that your bars and tone are exported as 16:9..) in the FCP Discussions!
(..NOTE*
BEWARE of sites found via Google which offer a QuickTime download ..these usually contain viruses, spyware etc whose aim is to hi-jack PCs, and possibly Macs too..)