I agree with you that there is a lot of marketing potential surrounding high quality water, no matter its form. But, at the same time, I believe that there are pizza operators who believe that water is a central factor in the success of their pizzas.
It perhaps will also not come as a surprise to you to know that it is not only the NY style dough where the benefits of the water are touted. For example, Marc Malnati, of Chicago deep-dish fame, has said that his pizzas cannot be made elsewhere in the country because he uses water from Lake Michigan. On the Neapolitan front, Naples 45, a specialist in the Neapolitan style in NYC, at one time imported water from Naples to make its dough. It eventually found someone, I believe somewhere in Pennsylvania, to chemically replicate the Naples water. I recalled that Marco (pizzanapoletana) addressed the matter of the water in Naples so I did a search and found this post: Reply 5 at http://www.pizzamaking.com/forum/index.php?topic=1795.msg17435;topicseen#msg17435
Of course, the major pizza chains that operate on a commissary business model tend to use water filtration systems. Papa John's does this with its American style of pizza, and it usually mentions this at its website. Mellow Mushroom, a growing pizza chain that also specializes in an American style of pizza uses spring water (originally it was Georgia spring water) to make its dough at its commissaries. It uses this fact for marketing purposes wherever it can.
In my own case, and as I noted at Reply 17 at http://www.pizzamaking.com/forum/index.php?topic=571.msg5913;topicseen#msg5913
, I could not tell the difference between various forms of water for the pizzas that I made.