UPnP (Universal Plug and Play) is basically a protocol designed to automate network settings manipulation or to discover other devices on the network (if they also use UPnP)
For example, if you had an Xbox360, and you would like to play online, the Xbox would automatically use UPnP to talk with your router, and tell him something like, 'open port X' or 'redirect traffic from external IP microsoft.com to my local IP in the NAT'. This is extremely useful for this kind of things, like video games, but unfortunately it's an insecure protocol.
UPnP has no authentication. Yes, this means that anybody in your network can force your router to perform those tasks described above (with a bad intention like opening your gateway(router) to the external network).
What kind of purpose would that serve for the operator (service provider)?
In theory, UPnP is useless for your ISP, since it is mostly used in the internal network and has no use from the outside.