I was trying to find out what these dates mean in terms of when the Industrial action would be if it happened, I found this link, workers rights regarding Industrial action and the rules that must be followed.
http://www.dti.gov.uk/employment/employment-legislation/employment-guidance/page18476.html
It contains lots of stuff about how you can't be discriminated against etc etc but in terms of timings I found this;
The union's first call for industrial action to which the ballot relates must be made before the end of the period of four weeks beginning with the date of the ballot or such longer period not exceeding eight weeks as the union and employer may agree. Industrial action to which the ballot relates must also first take place within that period.
If interpret that correctly it means that the ballot will be for dates within 4 weeks of the 3rd of December i.e. over Xmas/NY period !?
Though I may be incorrect, though it would make sense why the union have held off on the ballot as the action has to be within 4 weeks of the date of ballot so they could cover Christmas and New Year !
lots of other useful information on that site, worth a read and to know your rights as a member (rather than what the employer will tell you what your rights are).