The Police Ghost is an unmarked cop sedan built on the Stanier LE, itself a nod to real full-size American patrol sedans like the old Crown Victoria. Fans expect it back in GTA 6 as a stealthy chase car, but Rockstar has not confirmed it or shown it. This is series-based expectation, not fact.
No confirmed in-game name beyond series precedent, and no official way to get it in GTA 6 has been shown. Unmarked cop cars usually appear during higher wanted levels rather than being bought. If it returns, expect solid, balanced sedan handling for pursuits.
The community companion for Grand Theft Auto VI. Database, maps, guides and tools for Vice City and the state of Leonida.