Sony has confirmed that Remote Play between the PS4 and PS Vita will work only over Wi-Fi networks, but YouTube user The Phawx has discovered that Remote Play can work over a LTE / 4G network using a mobile phone that allows tethering. You can create a Wi-Fi hotspot on your mobile phone (like the Google Nexus 5 Android device shown in the video) and connect the PS Vita to it.
The video shows Resogun being played over the LTE network, which has a pretty slow connection of just 6Mbps, but the game is playable with some noticeable lag in input. It’s worth noting that the connection speed on PS Vitas with 3G may not be up to the job as the connection speed with be slower.