Hey, I think this is the place I'm most likely to get a sensible answer.
I hear a lot of complaints about tyres being tough to fit onto Campagnolo rims, generally regardless of which model. I think I have heard this said of other Italian rims. I have also heard that Italian rims have an ever so slightly larger diameter, which can make some makes of tyre hard to fit.

Is there any truth in this? What is the real cause? Do you notice it with your rims? I have to say that Schwalbe Marathons were a tight fit to my (French) Rigida rims.

I'm not inclined to believe that Campagnolo is simply mismanufacturing their rims.