I'm sure you've seen it a hundred times, especially on maps with lots of type. Labels and linework intersecting with each other, making the type difficult to read and the lines difficult to distinguish.
Here is a technique we developed at my office for dealing with these situations. It is an extension of a technique we used previously, that opens up a new aspect to the typemask.
First, place all the lines you want to "mask" (or block out) on one layer. If you want to keep these lines on separate layers, you will need a separate typemask for each layer, but it works pretty much the same way.
Now, copy all of your type objects onto a new layer. Lock the original type down so that you don't accidentaly modify it during this process. Any type object on this new layer will punch out the linework behind it. Select all of this type, and give it a stroke. The width of the mask will be equal to half of the stroke weight, so if you want to mask linework that is within a half a point of a type object, give the type a stroke that is 1 pt in width. I will typically use a weight between 1 and 1.5 points.
Color the type and strokes black. Group all the type together. Now move the group to the linework layer that you want to mask. Select all (all lines and the type group) and open up the Transparency Palette. In the menu that opens off that palette, select "Make Opacity Mask". Now uncheck the box that says "Clip" and your linework should me masked out.
NOW. Here's the cool part. You'll notice that the lines have been completely removed from around the type. But what if you just want to screen them back a bit - what if you want them set at 50% opacity near the type? Well it's easy! Instead of coloring the type and strokes black, just color them at 50% gray. Now when you make the mask, it will block out 50% of the opacity of the lines. If you want the lines at 30% opacity near type, just set the color to 70% gray. Super easy!
Also, if you want the mask opacity to vary throughout the image, you can do that too! Just remember, the parts of the mask that are black will block out everything below them, and the parts that are white will block out nothing, and all values in between likewise. You can even use gradients in your mask, leading to all kinds of possibilities for typemasking.
I used this technique in my "Barlovia" map to screen black lines around type back to 30% opacity.