When you hide an object on a layer that isn't the master layer in Maya, it will create an override that makes the layer respect the hidden object. Sometimes you don't want this, or you key-framed your animation on a layer that isn't the master and you want it to be on all layers. This script will fix that.
How to use:
Select your layer that has the visibility you want. Then select your objects that you want to set the visibility for.
And your current visibility keys/options are on all the layers!