GameSpot has a statement from EA explaining that the recently revealed tank concepts for Command & Conquer: Tiberium Alliances that look suspiciously like designs from Warhammer 40,000 were unintentionally exposed, and were never intended to be part of the upcoming MMORTS game:

"Games Workshop and EA are aware of the IP issues around the artwork in question, which have now been resolved," an EA representative said. "The artwork was internal EA concept art that was unintentionally released publicly. No Warhammer 40,000 tanks have ever made an appearance in Command and Conquer: Tiberium Alliances, and never will. Games Workshop and EA continue to have a strong relationship working together on Warhammer Online: Age of Reckoning and the new free to play game Warhammer Online: Wrath of Heroes which just entered open beta."