Hi,
I tried to get the spawners from a DungeonCrawl dungeon but if I retrieve the egg from a spawner that spawns a mob with armor and put it back in another spawner, the mob loses its armor. ( although I don't think the problem comes from this mod since they are vanilla mobs with armor )

If the retrieved egg is a regular Minecraft spawn egg (such as a Zombie Spawn Egg), then there's no issue.