I would like to think that somewhere in the vast galaxy of academic publications there is a paper examining the alphabetical distribution of Italian surnames, but if there is such a thing, it has not crossed my path, which means that instead of a learned explanation, you will have to put up with my inexpert ramblings. I would imagine that over a period of decades, perhaps, rather than years, the distribution of the surnames of the match officials for Serie A/B would match fairly closely that of the population of Italy as a whole, but given that there at any one time there are between 40 and 50 referees, it seems plausible that in any specific cohort there may be unexpected clusters of names beginning with particular letters. I started following Italian football in the mid-1990s, and I seem to remember at that time a plethora of referees whose names began with B (which would accord with JCFC's recollection), as well as several whose names began with C, including the above-mentioned Graziano Cesari, now gainfully (I hope) employed as the refereeing expert on the Berlusconi family's Mediaset TV channels, and the exaggeratedly monovocalic Cinciripini.
In recent years M seems to have become the most favoured letter, and I would not like to have been the appointments secretary when Marini, Mariani, Minelli, Marinelli and Martinelli were all plying their trade. At the present time there are nine referees who names begin with M (eight with Ma-): Manganiello, Marcenaro, Marchetti, Maresca, Mariani, Marinelli, Massa, Massimi, Monaldi, plus 6 (out of 16) VARisti: Maggioni. Marini, Mazzoleni, Merviglia, Miele, Minelli. Recently, however, C has been making a comeback, with Collu, Colombo, Cosso, Crezzini and Ferrieri Caputi joining the longer established Chiffi.
As in the UK, there are regional variations in surnames, complicated by internal migration over recent decades. Mostly these don't affect initial letters, but it is noteworthy that in parts of the North-East, especially in Emilia-Romagna and the Veneto surnames in Z are particularly common, this being ultimately a reproduction of the original local pronunciation of names such Giovanni and Giorgio. At the moment this isn't reflected in the Serie A/B list, the only Z being the vaguely Swiss-sounding Zufferli from Udine. And surnames with a prefix that looks almost like a definite article (Lo, La, Li) tend to come from Sicily (as with Concetto and Rosario Lo Bello), though Federico La Penna is from Rome