Infiltrator only bypasses Substitute and ignores the effects of Reflect, Light Screen, Mist, and Safeguard.
This means that Pokemon with Infilitrator (or No Guard) won't be able to hit Pokemon with Magic Bounce with a status move. However, if you use a Pokemon with Turboblaze, Teravolt, or Mold Breaker, status moves should be able to hit.
In addition, Magic Bounce cannot reflect status moves that were just bounced back by Magic Coat or another Magic Bounce.
In your scenario, Noivern would use Toxic. -> Magic Bounce activates. -> Mega Sableye bounces Toxic back to Noivern. -> Noivern is now badly poisoned.
You can also read more here: Magic Bounce / No Guard / Infiltrator
Hope I helped!