I posted this question on a few groups already. I've seen some various replies, and I'm gathering more opinions.
In the new SM Codex, the Librarius Conclave Formation (and also the datasheet that was released last year for Dark Angels!) has an interesting rule.
Short version: Nominate one Librarian to cast ALL powers that the other librarians in this formation (within 12" of the nominated dude) knows. If one Libby is within 12" of the 'master', he casts on a 3+. if 2 are within 12", he casts on a 2+. If you use this option, ALL Librarians (regardless of within 12") can't cast until the end of the psychic phase.
Emphasis mine, but you can guess where this question is going.
RAI, this means to say that the Librarians can't cast again until their next turn. To my knowledge there are no effects anymore that can be activated in another turn, during assault (I'm looking at you, Force), etc. To mix games, every Psychic Power is a 'sorcery', not an 'instant'.
RAW, I'm finding more and more people that are saying that 'until the end of the psychic phase' means that as long as everything else in that phase has happened, you can THEN start casting with those Librarians because now it's the end of your phase.
However, in the BRB, 'End of the Phase' is listed as 'after all other actions have occurred, before the next phase begins' (I'm paraphrasing from memory). So for instance, picking up the Relic happens at the END of the movement phase, after all movement, before Shooting begins.
So... what's your take on it? Are the Librarians unable to act at all for casting until their next turn, and GW once again failed to write a rule correctly? Or can they cast AT the end of the psychic phase?