As per their license, you cannot use them outside of UE4. This means that while you may be able to pull out the assets from your UE project and import them in Unity, it's not legal to do so.
Maybe you could use them in another engine if you show the Unreal engine logo on startup and pay for the licensing of the Unreal engine. (Though I assume other proprietary engines like Unity have rules against portraying their engine as another with the other's logo shown first.)
If you have money to get Epic to make an exception for you, you likely don't need freebies like these assets ;)
> This content is now available free of charge in the Unreal Engine Marketplace, where developers may download Paragon packs to use in their own UE4 projects.
So it's only for use in your UE4 project.
Per the linked post, they're only licensed for use in UE4.
You might be able to shoehorn them into something else, but copyright wise you're not authorized to.