A public test of the long-awaited network campaign co-op mode is going to be held in July. The ability to replay campaign missions will be tested by the studio.
According to a press email sent to The Verge, the alpha for both features will take place from July 11 to July 22. You can participate in the campaign portion of the game if you own the campaign portion of the game. You will need the Insider app on the console.
You’ll be starting the campaign from the beginning
Anything you have accomplished will not transfer over to the next campaign. You will be able to download a new campaign build and start the game from the beginning. Progress from the test won't transfer to the retail game when the updates are officially released. Crossplay is supported so you can play with your friends on all of the platforms. Four players will be able to play in a party.
We don't know when campaign co-op and mission replay will be made public, but 343 Industries said it will be in August. There is an open alpha of Forge for September.