My Alltel phone has an 'auto answer' option (Brad had Alltel)
You simply set it and the phone will automatically connect if it is connected to a 'handsfreee' devise (wired or bluetooth, depending on the phone).
My opinion is he simply called his cell from the home line at 6:40 am, answered the call for <30 seconds and then immediately drove to HT, arriving at 6:45 am. For those who question the time due to conjested intersections and stoplights, remember, this was 6:45 am on Saturday morning....traffic and light waits would be nonexistent.
I think the cell phone company's records would include info on which tower received the phone's signal. Since the house and the store are very close together, I wonder if they are served by the same tower?