I'm not a lawyer, but I am an accountant with about 25 years of experience in real estate investment and development. That's why I'm shaking my head over this. There are two possibilities:
1) they knew about the pollution and bought the place anyway. If this is the case, the purchase price should have reflected the cost of clean up. The only way I can see that they have a legal case in this instance is if they can document that the seller lied about the extent of the pollution. Even then they are going to have to explain why their own due diligence didn't uncover that.
2) they ignored the pollution and bought it anyway. As noted above, just about anybody could figure out the site was likely polluted. This scenario means the GB, or whoever made the decision, ignored the advice of somebody like me and went ahead with the purchase. I doubt they can win in court with this.
3) they didn't know about the pollution. This means, in essence, they are going to go into court and say "we're idiots and these bad people took advantage of us." This option might be the most entertaining.