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Millions of smart meters will fail when 2G and 3G turns off
(www.theregister.com)
This is a most excellent place for technology news and articles.
The software that controls them is absolutely terrible so I wouldn't be surprised if that is how they work.
But thinking about it it does seem really stupid for no reason so maybe what it is is the concern that if they do trip after 2G is turned off there's no way for us to know that.