Seems to be about 6-12+ months depending on sales/popularity. BUT-the intial prices on the cameras when they're 1st listed don't seem to be any better, & sometimes not as good, as the sale prices at various vendors. And Canon also doesn't seem to put their newly listed refurb dslr cameras on sale (with rebels usually being the exception) with the rest of their refurb cameras. Fyi, it seems to generally take much longer for a camera to be listed as part of their buy back program (Canon Loyalty program).
The 5DIII has been in their refurb store for a few months. The key is to make purchases during a 20% off sale. Things go mad fast- but the 5DIII dropped to like 2,200 for a few minutes before it sold out last time. Good times to buy lenses too!
In the US, go to the online Canon store, establish an account, and you should be able to get their e-mail notices sent to you. That's how I got on their list. I seem to get something almost every week, though it's not always about cameras and lenses, so I have to watch for those.