I was wondering about the same thing. After some digging around, I found that it's documented on the wiki that this feature is to allow for some monitoring via MQTT: Monitoring via MQTT
After enabling the MQTT Broker (without any security, just for testing) and configuring the MQTT Publisher to connect to 127.0.0.1, here's the three commands that I sent from a RasPi in my network and (from a different computer) what I got back. Router ID is redacted a bit.
root@raspberrypi:~# echo 'id' | mosquitto_pub -h 192.168.10.254 -t router/get -l
root@raspberrypi:~# echo 'name' | mosquitto_pub -h 192.168.10.254 -t get/1102600000/command -l
root@raspberrypi:~# echo 'uptime' | mosquitto_pub -h 192.168.10.254 -t get/1102600000/command -l
root@ubtest:~$ mosquitto_sub -h 192.168.10.254 -v -t \#
...so this is fully in line with what the wiki describes.