I am using this in a menu script to copy bones from one layer and pasting to another layer. I can only "copy" bones into a list from the currently selected layer. So I have to change layers in the menu script to "copy" a list of bones and their values and switch to another layer to paste based on settings in the menu script.
You can change all of the layers other values on and off. The stuff in the layer options when you double click a layer, but as far as I know you can't change the "eyeball" value on and off because it isn't an animated value.
Look at the scripting reference section for "MohoLayer" that lists all of the items you can change. Plus each layer type has other things that can be modified.