My wife's Z had this same problem a month ago. BBM was spiking to 425 mb of data and draining the battery. Have no idea why as she never uses it. I had subscribed her to a couple of wall paper channels in the beginning. Unsubscribed from them and she no longer has the problem. Which is weird because I am subscribed to 5-6 channels and have not had a problem.
Both of us on 3175
STL-4. 10.2.1.3175 w/ 1259 clock