I seem to recall a paper about using the noise in the electrical system of a home to determine what appliances were plugged in and turned on at any point in time.
Sidhant Gupta, Matthew S. Reynolds, and Shwetak N. Patel. 2010. ElectriSense: single-point sensing using EMI for electrical event detection and classification in the home. In Proceedings of the 12th ACM international conference on Ubiquitous computing (UbiComp '10). ACM, New York, NY, USA, 139-148. DOI: https://doi.org/10.1145/1864349.1864375
https://dl.acm.org/citation.cfm?id=1864375
That said: I used to work for a smart meter manufacturer and (AFAIK) we didn't do anything like that. Granular readings were the most important part. Our meters could report in 15 minute buckets, which was useful for tiered billing. Most of the push back against these meters were because they use radios to report readings back and there was concern about radiation. There were people who were building faraday cages around the meters.
