It seems like this mostly counts for the ones associated with the Colombo, Gambino and Bonanno families. It's not suprising to say the least as these families were hit hard by the authorities in the past and are tradtionally the most visible to the public. When they elect a new boss, it would not take long before everyone knows it.

However, the Genoveses are very secretive when it comes to initiation ceremonies, which explains why they aren't mentioned. This probably doesn't count for them.