If you completed Maxis's side of the easter egg, you get all five perks permanently. This means you do not lose Tombstone when you retrieve your stone where you died. This is a reward for sacrificing the usage of your perks to turn off the power during a step to his side.
If you completed Richtofen's side of the easter egg, the fog and denizens would disappear. All the teleporters would be permanently open as well to compensate for the disappearance of the denizens. In addition, the lava pits across the map would crust over, allowing safe passage through every part of the map. This is a reward for dealing with the denizens while traversing the whole map to search for the Jet Gun parts.
Now, in these cases, it would also be possible to have both rewards in a single game if two different players in a lobby had completed the two different sides. This would be evidenced by the spire being able to shine both orange and blue/purple at once. In order to not make a new Zombies match with these two rewards too easy, you'd have to make it to Round 25 to get the rewards, similar to how in Nuketown Zombies, you'd have to make it to Round 25 before Richtofen becomes the Demonic Announcer.
Anybody like this idea? =D