said by innoman:
Actually... they happen almost constantly... as least it would appear that way if a human is looking at the log files (I have done a great deal of this on many devices). There are measurement reports, location/routing area updates, paging requests, handover requests, cell reselection, acknowledgments for everything, etc... A device has to talk to the network often or it won't know where to send the page requests if someone calls it. In UMTS, coverage for each cell site grows and shrinks (it's referred to as cell breathing I believe) based on the number of users, network conditions, etc... to prevent interference, saturation, etc.
But should all those "behind the scenes" data transactions be counted towards a users' data bucket? No. This stuff happened long before there was 3G data and nobody was charged for it.