XP1 was, if I recall correctly, the first photochromic (I think that's the right word) B&W film, using the C41 chemicals normally used to develop colour negative film. The consequence of this is that the developed image on the film should not be metallic silver, but based on dyes instead. As a result, it should be posible to use Digital ICE on such films - in fact, it is why I sometimes use XP2 today, simply to avoid all the retouching.
As an experiment, it might be worth not specifying B&W in the scanner software; scan them as colour negs, then convert to greyscale later on.
With my scanner, a Nikon 8000ED, this isn't necessary, but perhaps the Epson software is doing things differently.