I agree - but I think the point here is that it isn't really an advantage because it actually discourages the other side entering into negotiations, or at least gives them cover for doing so. ACL can now, quite rightly, say there's no deal to be done at the moment and we're not going to talk about one until SISU stop threatening our business.
Fwiw I negotiate a bit in business, as do more than a few others here I don't doubt. Not for multi-millions, I should add, but the basic principle is that you've at least agreed to negotiate before you start. At the moment this is holding even that agreement back, and from a PR point of view it's a disaster too. PR matters to both sides here because it can bring pressure to bear.
If I was being ultra-cynical, I'd say this might actually be a bit of an own goal. ACL, council-backed and presumably safe for the short-term, can watch SISU build mounting losses in the hope that either they see sense, or give up and sell to someone who does. What threat there is from the court case has been reduced from the absolute humping that SISU got last time around. So the pressure on them to do a deal that might not make them much financially, is actually reduced by SISU continuing the action.
SISU, in the meantime, have lost most of the goodwill they've so carefully tried to cultivate of late. And this to give them an "advantage" that they're almost certainly going to have to throw away before they can actually get to the negotiating stage.
Regardless, good negotiators in my experience, manage to come to a deal that suits everyone, and gain something out of it for their side. Sometimes you get more than you expect, and sometimes you get less than you really wanted, but if you fail to do a deal because you're being pointlessly boneheaded then that isn't good negotiation, it's stupidity (imho).