No they can’t. Obsidian talked about it. Using unreal is why the Outer worlds had separate levels and lots of load screens.Technically any game engine could handle that if they decided to track each object. It just makes more sense to restore areas of the game world back to a target state for stability reasons to avoid some of the fukked up situations that happen in Bethesda games. Given the effort they could recreate that system in Unity or Unreal.