Can a sigma 28-105mm F3.8-5.6 UC-III lens that was for a 35mm camera fit on a prosumer digital camera?

Most 'prosumer' cameras have a fixed lens, so there is absolutely no way you could interchange lenses.

If you actually mean a 'digital SLR camera', then yes it could fit, depending on the lens mount used by the camera.
According to the Sigma webpage, the lens should fit Canon, Nikon, Minolta and Pentax digital SLRs with an AF mount (in which case you still might have to buy an adapter).

check out the chart and sigma lens page below...

and perhaps you should also email Sigma so that they can give you a definite answer.

It should fit, assuming the mounts are the same.

You will have to buy the right mount of the 28-105mm lens. For Canon its a EF mount for Nikon I believe its an AF mount.

If it's Nikon or Canon AF compatible it should. Consult with a dealer.

It will, however, become a 35 to 160 on a digital slr.

Different cameras have different lens mount. You need to check what type of lens mount of the camera you buy, and also check what type of lens mount of the lens. If they are the same. It will fit.