It's mostly in russian, but I can post here some facts from Tiberium Alliances developers:
- Tiberium Alliances takes time part between C&C2: Tiberian Sun and C&C3.
- 90% of all battles are vs Forgottens, that want fully infested world, GDI and Nod will clean territories, fighting vs Forgottens and sometimes they can ally with other alliances from GDi and Nod to fight against enemies
- there are no story, and as developer said, players writing sort of story, creating alliances and fighting against others for territories
- they will tell us about story more, when open beta starts. But shortly, center of the continent is infested with Forgottens, GDI and/or Nod will onquer territories, moving through Forgotten bases to the center of the continent