This is an extremely important case, in that it underlies a central concern in scientific reporting, and it threatens to change the risks associated with scientific innovation and communication. For instance, if scientists at a pharmaceutical company issue unfounded assurances that a drug is safer than it is in truth, consumers might have a reasonable case. On the other hand, predicting earthquakes is so difficult, even if the scientists had mistakenly suggested that there was no reason to suspect an imminent quake, I find it hard to find justification for a 6 year prison sentence, in addition to damages.

But beyond that, it seems the scientists offered no such assurances at the meeting in question. To quote the Nature article (perhaps biased in favor of the scientists):

The minutes of the 31 March meeting, though, reveal that at no point did any of the scientists say that there was "no danger" of a big quake. "A major earthquake in the area is unlikely but cannot be ruled out," Boschi said. Selvaggi is quoted as saying that "in recent times some recent earthquakes have been preceded by minor shocks days or weeks beforehand, but on the other hand many seismic swarms did not result in a major event". Eva added that "because L'Aquila is in a high-risk zone it is impossible to say with certainty that there will be no large earthquake". Summing up the meeting, Barberi said, "there is no reason to believe that a swarm of minor events is a sure predictor of a major shock". All the participants agreed that buildings in the area should be monitored urgently, to assess their capacity to sustain a major shock.

To continue the analogy with medicine, it seems similar to a group of scientists suggesting that a particular course of treatment is likely safe, then receiving blame when the treatment goes awry. But blaming medical researchers, or earthquake scientists, could discourage innovative new treatments.

As one final point, I'd point out that the occurrence of an earthquake does not disprove the scientists: the likelihood of an earthquake given the data could still have been small, just non-zero. If medical researchers were held accountable for every death resulting from heart transplants gone wrong, we'd never have the overall benefit they provide.