I am happy to be proven wrong but I wouldn't hold my breath if I was the TWU, I find it hard to believe that the High Court will uphold any decision that removes the right of a company to determine who it employs to perform certain work, even if we don't agree with contracting out.
Pretty sure this is not about who they choose to employ, rather the process and manner in which a large section were dismissed and under what pretence. The court is deciding on whether the dismissals were conducted in an appropriate manner, and if not, what penalties/compensation is warranted. If it was about whether they have the right to dismiss them or not then there would be an argument for reinstatement.