I once put this very question to the Fasting Doc on the Fasting Connection Forum, and he confirmed that fasting does indeed clear out arterial plaque. When the body starts to run low on its usual sources of fat, it will look for alternative sources to consume before it starts to breakdown protein for energy.
The fatty deposits that line the epithelial layers of our arteries, etc., are just such a source of fat. For this reason, arterial plaque is usually only targeted during the latter stages of a prolonged fast. Also for this reason, I doubt that anything less than 30 days will make much impact.
If/when the site is up & running again, I'll see if I can find the doc's reply & post it on this thread for anyone who is interested..