Some multiplayer games offer cross-network play (or cross play), which enables gamers on Windows 10/11 devices and Xbox consoles to play with gamers on PCs, Nintendo consoles, Playstation consoles, and more.
Yes, Call of Duty: Modern Warfare 3 has full cross-platform support. This means that you can squad up with players on any console  PlayStation, Xbox, or PC  and enter the battlefield together. This is true for any online mode in the game.