It all comes down to the quality of the submitted picture and, to a certain extent, the circumstances shown in the image. There is some leeway for older photographs for example - the Screeners do not expect a photograph taken in the 1950's to match one taken with a professional Nikon or Canon in 2012. There is still a quality bar to cross however, even for older images. Not a factor in this discussion as there were not many camera phones back then!
For a modern image, the device used to take it is irrelevant to the Screeners. If the image meets the acceptance criteria, they will accept it. It does not matter if that image was taken on a camera phone, a DSLR or a low end point and shoot. The device used to take the image will be important to the uploader however, as it determines the starting quality of the image they have to edit. A plus point in this day and age is that you can always have a reasonable camera in your pocket if the one on the phone is good enough.
It would have been unthinkable to have camera phone images accepted in the past, but as the technology improves there must come a point where they become good enough. I guess we are just getting there, but I bet the acceptance ratio will still be low for such devices for some time to come.
Erm, is this thing on?