I've seen LiveU in use. It utilizes a bonded cellular system. It delivers broadcast-quality audio and video to the point where you cannot tell that it's not traditional ENG (or SNG for that matter). The latency is sometimes very high (around ten seconds)! This will replace a lot of the mobile uplinks for affiliate work. I don't believe you'll see the Superbowl using this technique, though. Also, like FaT Air says, not every area in the US is served well by cellular. I'd say it sounds like a plausible backup to a traditional uplink, but the big boys already have full redundancy built into their trucks.