Funny ships, those. It's a safe bet every other naval power looked at that and said "huh, why didn't we try that?"- whether it really worked out well or not is hard to say, though. The increase in range and angle of shot at longer ranges was definitely improved, and on at least a couple of occasions those guns as a result made life very difficult on Mediterranean operations. On the other hand, I've read that Italian guns tended to wear out far faster than contemporaries. For the Italians, that probably wasn't a big deal- their plans called for operations to be limited to the Med, so they never were far from home (thus the low fuel capacities for their ships as well), so guns that wear out fast probably were just seen as one of those 'feature, not flaw' things.
I'll note that this was referencing Italian naval guns in-general, and not just the bored-out guns on the Cavour/Doria class ships, in the interests of being fair. It's interesting though that only the Italians tried this boring-out trick- other navies, already using 14-inch guns or larger, probably didn't really have the need outside of the French dreadnoughts, the USS Arkansas, the Soviet Ganguts, and the occasional oddball like the German predreadnoughts. But to my knowledge, none of those navies ever really looked into a change to the ships' existing guns.
