Individual mafiosi had plotted against one another from time to time. Certain men in the hierarchy have plotted takeovers. etc. But these have mostly been "Intra" family, not between families. On the few occasions through history where there were plots between families, these were all accomplished or attempted surreptitiously. NEVER conspicuously.

That would be the equivalent of "declaring a gang war" on another entity. That never happened. Ever! It would mean total annihilation.