The holofields are options, not standard, in the latest codex I have (it's old, very old), any my application of optional gear on vehicles in this thread has been, and will probably continue to be limited to filling extra space on designs that need to use up tonnage.
That being said, I gave the Fire Prism an ECM suite specifically for that, intending it to be used to produce Sensor Ghosts, which seems like something similar to what holofields do, if not quite the same.