Night Fighting screwing with Necrons? We have 2 units that can shoot over 24". And it makes us virtually invisible to enemies with longer range weapons until we decide to step forward and shoot them. If it really bothers you, take Solar Pulses to cancel the Night Fighting on your turn.
As for the original question, the important part of the rule is as follows.
" ... whilst the Night Fighting rules remain in play, roll a D6 for each unengaged enemy unit on the battlefield ..." (Page 55, Codex: Necrons)
This would indicate that even Allies of Convenience or Desperate Allies can be struck. This is in fitting with Necrons though and how they view all other life. They don't care if you survive the battle, so long as they win. Of course, some players could have the misfortune of striking their allies but not the enemies.
"Fetch me another plaything. This one seems to have broken." -Urien Rakarth
Space Marine- "This planet is ours, witch."
Eldar- "No ... This planet is theirs ..."