Is there IED system working for mods such as ACE? I've noticed some IEDs and VBIEDs placed, but have yet to have one explode.

If you're using ACE, you need to set the IED module to third-party, but yes it works. Can most certainly confirm it works.

The 3rd-party checkbox is as far as i know just a placeholder for now. Normal ALiVE IEDs are configured to be detectable with a ACE minedetector, but disarming them is still just a normal interaction. Nothing is tied to ACE Explosives, yet. I will start tinkering with it and get the IEDs fully ACE compatible, soon™.