What are the Van Saar ones called? Those ones.Not Thermal Mines then (which have different mechanics than melta traps)?
That's just a distinction without a difference.
Cawdor (not Redemptionist) Juves get a rule that allows you to add d3 of them to your starting crew, even above the maximum. I'm really glad they added a way to represent the horde aspect. Sure, they're garbage fighters, but extra bodies are extra bodies.
Edit: And it looks like the gangers get a rule that allows you to bring one extra of them!