Não houve encontros com os Borgs já ocorridos na Zona Neutra antes de Q Quem?

SIM

Os encontros de Borg eram conhecidos pela Frota Estelar, mas a informação não era geralmente conhecida em toda a Federação.

Da página da Memória Alfa no Borg

As of "Q Who" and "The Best of Both Worlds", it appeared that Starfleet had never heard of the Borg. Subsequently, Star Trek: Enterprise's "Regeneration" and Star Trek: Voyager's "Dark Frontier" showed that not only was Starfleet previously aware of the existence of the Borg, Federation scientists actually pursued them – even if they were considered mere rumor. Further, although Guinan indicates in "Q Who" that her people were attacked by the Borg, it is implied that Starfleet was not aware of the threat. However, it was later revealed in Star Trek Generations that Starfleet, in fact, rescued the El-Aurian survivors of the Borg attack including Guinan, and it seems unlikely that Starfleet would not inquire as to the cause of their plight.

Se ninguém sobreviveu para relatar o encontro, ninguém na federação saberia sobre o encontro e Guinan está na federação.

Se bem me lembro, embora os borgs não dilacerem planetas, eles assimilam, assim, se os borgs atacassem o planeta classe M, eles ainda estariam presentes e assimilariam questões biológicas e tecnológicas.

Os borgs teriam aprendido sobre a humanidade e a Federação quando eles assimilaram os pais de Seven of Nine em 2356.