Even though I have had NFL Sunday Ticket since the first year they offered it (the curse of being a Connecticut Rams fan) I never called for a discount.
This year due to unrelated reason I was on the phone with them and they looked at my history with them and volunteered to give me this season for free. They told me they looked at the prior years and are giving it to me free due to those records.
It may just be they (AT&T) are looking at prior year records closer then DTV did. Sounded to me in my case it was due to them never giving me a discount in the past for Sunday Ticket.