Yes, if you process the raw file in Lightroom 2.5 (not 2.6 RC) you can have a wider scene than the Canon 28mm rating.
Save it and open it in Photoshop CS2 or later.
Use the Distort\Lens correction filter and crop it as wide as possible.
And the resulting file is wider than the Camera JPEG !
Have a Nice Day.
Thierry