RMT's case revolves around the fact that the British government didn't give any sort of preference to Bombardier or do anything to protect jobs in England.
It's good to see the unions take a break from whinging about public sector workers having to share some of the pain of budget cuts and redundancies with private sector workers but their legal action is futile. Under EU law it is illegal for the British government to give preferential treatment to people or companies in this country over people or companies in the EU. They would be breaking the law that their masters on the continent have passed down by doing anything protect our interests, save jobs or keep taxpayers money in this country.
So yeah, good luck RMT and let's hope the media give as much attention to the failure as they have to this announcement.