It has to be presumed, or the Kill Warrant Scanner makes no sense.
That can be explained through an automatic data dump to/from Nav Beacons or Stations.
When a ship arrives in a system, it links with the nearby Nav Beacon and they synchronise various databases which can include warrent information. Given the rate at which NPC ships appear, new information will be spread throughout known space pretty quickly.
There will be edge-cases - someone returning from deep space encounters a pirate before reaching known space will still get recent warrent information (AFAIK) - which can be treated as a practical implementation limit. However this could be "fixed" by recording timestamps against information and for the last-sync - the problem then is that you have to keep outdated data alive undefinitely.
Quantum entangled particles would only provide comms between predetermined, not arbitary, end-points. It's analogous to two tin cans and a piece of string. Sure you could build up a network across which messages would be relayed, and it would then explain your relationship to your last port of call.
The only thing I see in the game which requires superluminal information are sensors and comms when in super cruise - which, as I mentioned above, are practical compromises for the game (and could be fudged with SC-physics).
Frankly though, restricting to non-FTL comms has more interesting consequences than allowing f ree FTL comms across the universe.
As for the OP - Player groups can set up team speak groups themselves, without the involvement of Frontier. So why would Frontier spend effort here when they have plenty to do already?