I am not sure how you have made your estimate but I could confidently say that over the whole country in Italy the split would be more likely 90% wood only and 10% gas assisted (most likely not to burn wood/gas mixed because they may have gone gas for local restriction...).
In Naples, counting the thousands of existing pizzeria probably you are luckily to find 1 or 2 gas ovens (only ever seen one at a demonstration not in an actual pizzeria).
With Gas only you would not necessarily need a chimney, while a wood.gas mixture would suggest a scenic factor other then somehow try to help in keeping the floor balanced...
Ciao
