This sounds like a bunch of garbage to me from AT&T...
*+They establish a data connection with our network and keep it open even if there is no data being transmitted. If the customer does not end their data session, it is recorded during a nightly feed to the billing system. The data session can contain billing for all the data that was transmitted throughout the day.+*
So if I am to believe this, AT&T accumulates all data usage throughout the day and bills it in a chunk overnight? Then why 2 and 3 chunks? Why not one? There is a huge flaw in their billing and recording of data usage then. It's like a lawyer taking a case and billing the client 24/7. Nothing is itemized so how do I know the correct amount is being billed? How do I know the data session was ended properly?
*+Push capabilities are common with many social networking (Facebook), news, weather and e-mail applications. Push capabilities provide real-time data transfer as it is made available, (e.g. weather or news alerts occur in real-time as they happen and are ?pushed? to the device which consumes data). If the phone has push notifications active this may result in an open data session. To capture ongoing data consumption records, our systems are designed to send all accumulated data after a predetermined time each night.+*
So let me see if I understand this. I am getting a pushed a notification. My connection fails, AT&T knows my connection fails but continues to download all the data? I'm supposed to believe AT&T is storing all this data being pushed to me!!! WOW - - THAT IS TOTALLY A LIE!!! Push items are the app's server holding the info then sending it to the device. The cellular network is just the gateway to get it there

Just like your wifi hooked up to your modem is the gateway.
Now that I think about it...
This also means Apple's push notifications is flawed and skewed to the advantage of the AT&T and now probably Verizon. When the phone goes to sleep, wifi is off, if push is on, it is receiving data on the cellular network and not wifi? WiFi is off to conserve the battery and stick the consumer with high data usage. Why the heck would I even want to use push notifications then if my data is coming in over the cellular network in my home with wifi?
Oddly enough, and we've done nothing different, the mysterious data usage has stopped. I am now into 13 days of the billing cycle and it shows only 8% of the allowed 200mb used so far. It is now back to what it has been every month since she got the phone last August. The only thing I did was threaten AT&T to reset usage on the phone at 12am the start of my billing cycle, screen shoot it and email it to myself. Then do the same at the end of the billing cycle, which shows the date plainly when I reset it. If her phone didn't agree with the billed usage, the FCC would hear about it.
If Apple really wants to do a major upgrade to the OS, time for a tight data usage monitor, wifi sleep or not, push restrictions by connection type, and a priority force to wifi ending a cellular network connection when a wifi connection is present and allowed use.
Tom