The BBC realesed the new sypnosis for the Sontaran Strategem...so here it is:
Martha Jones summons the Doctor back to modern-day Earth, but with the mysterious ATMOS devices spreading across the world, Donna discovers that even her own family is not safe from the alien threat. Is it too late to save them?
And next on Wikipedia this was said but as wikipedia is known to be unreliable just treat it like rumours:
Having covertly established a base at the mysterious ATMOS Factory aided by the Rattigan Academy, the Sontarans unleash a potent terror which brings the world to its knees.
Also you might notice I am now being funded by Atmos on my site..........hehe