Actually, Marcella Hazan "popularized" the "no cheese with fish" rule long before Scott Conant did, probably even before he was even born. (Unfortunately, I can't find the quote right now.) But even she allows exceptions, such as her tortellini with fish stuffing, which includes Parmigiano-Reggiano.
I believe "rules" are made to be broken, anyway. If it tastes good, it is good. So I mix ethnicities with abandon.