Here's what I know. The problem (in my case) is connected to Corp Sync, which I use to sync Hotmail.
3G communicates virtually non-stop (in blue mode, not white), and the bulk of the traffic is received by the Pro, not sent.
The phone runs very hot (today was over 107 degrees) and com.Motorola.service.main shows as the service hogging battery life.
I deleted corp sync and rebooted. 3G activity dropped to nil, phone temp dropped 15 degrees and battery seemed to improve.
Waited 30 minutes, re-added corp sync. 3G activity returned to non-stop and battery temp raised 10+ degrees.
In just 20 minutes or so, it's already received almost 5meg of data.
I don't what is being sent to the phone, because my Outlook Hotmail Connector on the client is set to only sync changes once every 30 minutes.
If I can isolate what's happening, maybe I can come up with a permanent fix.
I'm hoping power users who know more about these items may have a suggestion or two, meanwhile, I'll research further.