removeAllDisplayVisiblityOverrides();

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.

DOWNLOAD:

removeAllDisplayVisiblityOverrides.mel

How to use:

Select your layer that has the visibility you want.  Then select your objects that you want to set the visibility for. 

type removeAllDisplayVisiblityOverrides();

And your current visibility keys/options are on all the layers!