Crossplay

Is Cities: Skylines - Mass Transit crossplay?

Crossplay does not apply to Cities: Skylines - Mass Transit: it has no online multiplayer.

Mass Transit brings several new systems into play to help citizens traverse their towns in speed and style. Commuters can now get around on the water, up high mountain peaks, and even through the sky thanks to the addition of ferries, monorails, cable cars, and blimps to the game.