If I were head office staff at BASSA/Unite I would be very concerned as to the possibility of damages arsing from the threat of strike action.
As has been mentioned above just the fact of balloting on an issue, where the company can legally prove it has explored all avenues, will cause a damages claim that could potentially run into hundreds of millions.
Money which I would be fairly sure Unite can't afford to risk.
The only road for strike action is one that has been tested thoroughly for legal 'water tightness' and proven not to leak. At the moment the BASSA case seems to resemble a colander with lots of extra holes in it.
It will take mighty balls to strike in the current climate with a case so leaky.