A sincere question: why they don't place some relay/repeater for the robot's signal so they could control it from anywhere in the world through internet (or even some very private wireless communication network, outside internet due to security concerns)? The fact that they have to switch personnel every 15 minutes is a sign that they're doing this in situ, rather than remotely.

Drones with mobile network connectivity are already a thing, for example. If you consider that internet exposure is dangerous (connection could be hacked, etc), ham transceiver repeaters are also a thing, and you can even chain many of them across many kilometers. It's called mesh network.