WMG: Star Trek: The Next Generation/Doctor Who: Assimilation²

Q will ally himself with the Federation against the Borg and Cybermen

Qs are time lords. Gallifrey is the Q-Continuum.
Obvious, really.

Gene Roddenberry is a Time Lord
Hence why Star Trek is able to simultaneously exist in a parallel universe and be a TV show that Rose (and Izzy) have previously referenced.

Guinan is a Time Lady
Go reread her conversation with the Doctor, it might as well be official.

The events of the crossover indirectly lead to Star Trek: First Contact happening
It's all too easy to extrapolate from the end of the final issue, with the Borg stating that they intend to master time travel as a result of their experience with the Cybermen and the Doctor. Kinda makes the whole thing a bit of a Nice Job Breaking It, Hero moment for the Doc...

The merging of the Star Trek and Doctor Who universes is Decade's fault.
You know it is.

The reason the Cybermen in Nightmare in Silver are like the Borg is due to this encounter

The reason Star Trek is Fictional in the Whoniverse is because the thoughts of the writers tuned into events of the other Universe
  • Like with Earth-1 and Earth-2.
    • Likewise while not common knowledge anymore Doctor Who was once a television series on Earth, even to this day it's a cult Holo program series.