If Merseyrail communicated why the heaters were turned off to passengers then there would be no need for the story to be reported. However, I wonder if they didn't and passengers wrote in to the paper to complain about their journey on cold trains.
The heaters would have been replaced during refurbishment or even before if they'd been considered to be potentially 'dangerous'. I don't see how they would have been 'missed' as a previous poster puts it. Surely after 30 odd years service with the same operator Merseyrail knows the construction of its trains inside out.