Same problem here, except I only fly 42-300. Couple of years ago my outfit tried to persuade ATR to put all-engine climb gradient tables into FCOM 3. Some time has passed, there was no mail from Tolouse so we went to our performance boys and they've printed out tables from their performance software. So while we're waiting for major FCOM revision, these tables are inserted in FCOM binder behind chapt 3.04.05 as temporary solution.
My guess is that ATR was so embarrased by -300 climb performance that they want to keep it secret.
