Re: Garden ops local multiplayer
This is directly from the EA site : http://help.ea.com/en/article/coop-pvz-garden-warfare/
"If you have an Xbox One, you have both the online co-op experience of Garden Ops and an exclusive offline co-op mode! Xbox One uses split-screen to allow you and a friend to stand off against waves of zombies and fight for the glory of your garden!"
According to this, you can play normal Garden Ops co-op with others online and the offline co-op which I would imagine is where the split screen comes into play. So I do not believe you can co-op splitscreen online, only offline as indicated.