If all else fails---------this will work. Get a Dremel tool and chuck in one of the thin cutting wheels. Simply cut thru the cup. It wont matter if you grove the BB when doing this. A small cut in the BB thread will make no difference. Then as I say before you put in a new bearing cup, chase the threads with the proper tap. You may have to take it to your LBS to get this done.

BTW one cut thru the cup on one side should be enough to be able to loosen the cup enough to get it out with channel locks squeezing down the size of the cup. If not cut another thin channel 180 degrees opposite the first, then the cup should fall out.