YouTube user The Phawx has tested the viability of remote playing a PS4 game on a Vita using a mobile phone's LTE network. The takeaway: it's surprisingly functional, even tested in downtown Manhattan.
Prior to making the video The Phawx had to link his two Sony platforms together at home. Once he set up a wireless network via his T-mobile cell phone, he connected his Vita to it then launched the Remote Play feature. Initially the Vita will want to connect to something locally, so it takes several seconds before it opts for plan B: the PS4 that's been tethered to it prior. In The Phawx's case, his console was about 10 miles away at his home.
Further details about this test: The Phawx's LTE netowrk was getting about 38 milliseconds of ping with a downloading speed of roughly six megabits per second. Once he connected his Vita and tested his connection, it amounted to a downloading speed of 5.7 Mbps with an upload speed of 1.8 Mbps.
Upon testing Resogun under these conditions, the Phawx estimated that he was experiencing a 150 millisecond delay, which isn't ideal, but is still playable. He also noted that he was getting closer to download speeds of 10 Mbps when he attempted to test his network's strength upon standing, but for whatever reason it wasn't as strong when he set his phone down on a slab of rock. The point is these conditions were very far from ideal, but the results were serviceable, suggesting that in many other conditions it will provide an even smoother experience.