Pull Request Preview from branch on fork

Is it possible yet to create PR previews from PR’s instigated from a fork of a repo?
To contextualise, I work in an org and we fork the repos we work on to our private accounts. We then make PR’s from branches on our fork’s back to upstream. Is it possible that I might achieve this with the Preview Environments?

Hey James,
You know, that’s a great question. However, I’ve just verified that a PR from a fork of a repo made back to the original repo does not trigger a preview environment to be created.

If you pushed back to the fork, you could have your own PR environment based off that though.

John B