I'm in an early game where my backwater is being used as a freeway by Astro Trains, and so I fiddled around with the line place mode and set up a string of CDM turrets like XMas lights between two wormholes.
"That's cool," say the trains, and fire straight through 'em.
Am I missing how these are supposed to work? Per their description, they should be like dead zones, where any dark matter being fired through them instantly dissipates. You should be able to set them up like a big fence if you want to. Or do they act like force fields, only protecting units inside their range?
Images:
http://imgur.com/a/A6r1SSavegame: