Surely the statute of limitations on this has passed now and we can know who these legends really were? Perhaps encourage them to seek legal advice about revealing themselves.
Criminal charges don't encompass the entirety of the potential consequences for the "perpetrators" revealing their identities. Go through a long list of famous people or people you know and ask yourself "how would their lives be impacted if it turned out they did the Max Hedroom hack". For many it would probably be inconsequential or likely beneficial, for some it would be disastrous. Consider, for example, if someone was working a job with a high degree of responsibility, perhaps involving security clearances, would they want to risk disclosure?
I was going to reply indicating that criminal law has no Statute of Limitations but that seems to be a Canadian thing. In the US it has to be considered a "Heinous crime". I'm certain under modern light of what hacking has become they'd likely consider this relatively innocent event heinous by modern standards.