Activision in its infinite wisdom has completely neutered the PC version of Call of Duty: Infinite Warfare, where the game will not work between Windows Store and Steam - yeah, so if you buy it on the Windows Store you cannot play with your friends who purchased it through Steam.
The official Activision Support website details it well, with both Call of Duty: Infinite Warfare and Call of Duty: Modern Warfare Remastered not having any support for crossplay, with not just the Xbox One version of the game through the Play Anywhere program, but the Windows Store and Steam versions of the game.
Is Call of Duty: Infinite Warfare or Call of Duty: Modern Warfare Remastered an Xbox Play Anywhere title?
No, these titles are not under the Play Anywhere program. If you purchase for Windows 10 on Windows Store, you will only be able to play on your PC. If you purchase on Xbox One, you will only be able to play on your Xbox One console.
Can I play Call of Duty: Infinite Warfare or Call of Duty: Modern Warfare Remastered for Windows 10 on Windows Store with my friends that are playing on another PC platform?
No, you can only play these titles with other users of Windows 10 on Windows Store.
Seriously, Activision - what the f*** is this? Microsoft: you need to sort your Windows Store out right now, drop the act - it sucks, and you're not just watering down the PC gaming industry, you're urinating all over it. This makes Windows Store something that should be completely avoided at all costs, period.