It's called the "lawsuit lottery" for good reason.
I've been involved in lawsuits - on both sides - and based on those experiences my total disgust for lawyers is completely justified
. However, while being involved in a lawsuit is extraordinarily unpleasant, it can be a learning experience. Among other things, I had more than one lawyer tell me (in so many words) that they hate having engineers on the jury because we tend to look for facts and logic, while the lawyers (especially in tort cases) try to appeal to emotions.
I'm surprised that, at least according to the reports I've seen, BA is not listed as a defendant. This violates rule #1 of filing a lawsuit - you list EVERYONE who has any possibility of being liable. You see, it's really easy to drop someone once the lawsuit is filed if it turns out they have no liability - but it's all but impossible to add someone who turns out to be liable - you basically have to quit and start over again.
If it turns out (and I'm just hypothesizing here - not trying to impugn BA) that mandated inspections were either not done, or not done correctly and existing cracks were missed, GE/Boeing can simply say 'if BA had done what we told them to do (and what the AD mandated), this never would have happened' and they're pretty much off the hook. The lawyers will need to go back and start over again.