On the topic of Battiato vs Ferretti, I believe that both insert historical references, but Ferretti does so with a more social twist, while Battiato, in his "own" search, appears to be less secular. However, this aspect is not where the comparison lies; rather, the result changes when evaluating the overall song. In PGR, the lyrical dimension consciously prevails over the musical form; GLF’s voice is an instrument and the main instrument in the PGR ensemble. In the time of CSI, he didn’t even grant space to Ginevra di Marco, using her voice as a musical counterpoint to the male voice, trivializing it, much like a salad to garnish a dish... sometimes it fits well, other times it makes it heavy and pompous. This concept can be proven by listening to the latest "d'anime e d'animali," realizing how the departure of the "magnellophoni" and the warbling of chirps have lightened and made the music and singing flow more quickly in that album.
As for Battiato, on a common thematic research basis, the result diverges from that of PGR due to the purpose and the position that the lyrics find within the overall song structure: the point is that here the texts are not written by Battiato himself but by Manlio Sgalambro, poet by profession, and in my opinion, this pairing works better as a final result when compared to the famous precedent of Mogol/Battisti rather than with PGR.
In Battisti, the lyrics were important as well, and the voice, like in Battiato, was a prominent instrument, but the interesting thematic research in Sgalambro and "musical" in Mogol hardly overshadows the music of the main authors and performers in the final result, as happens instead in CSI/PGR (much less so in CCCP). After all, Ferretti, Battiato, and Battisti are/were all strong personalities, central figures with a significant ego, and while the former puts his "instrument" at the center, the others appropriate the "means" of others to make it their own, so it is obvious that they do not highlight it in comparison to their central work, which is to create music.
In conclusion, simplifying and perhaps with a hint of banality, GLF cannibalizes the PGR with his voice, while FB and LB vampirize the "great" work of others to enhance their own.