The Pottermore post announcing the game does not mention Niantic at all.

The sign up page for harrypotterwizardsunite briefly mentions them, as well as some expectations for gameplay.

Harry Potter: Wizards Unite uses state-of-the-art augmented reality technology to reveal the magic all around us. Explore real-world neighbourhoods and cities to discover mysterious artifacts, learn to cast spells, and encounter legendary beasts and iconic characters along the way!

And of course the Niantic post mentions everything except portkey.

The information we have now is scarce, but it is totally in the realm of possibilities that just the location data is being shared between companies.

Also remember, it is totally possible for a company to have more than 1 dev team, and that Niantic just absorbed a dev team from Evertoon.

Keep your hopes up and lets give the game developers some positive feedback on what we hope this game will be and what we dont want to see repeated from Ingress or Pokemon go.