to my knowledge Cingular has never had a no credit check policy on 'regular' contract service plans. They do however, on occasion, lower credit standards based on the current goals of the company. an example would be if there was a huge focus on adding new customers and they need to make up some lost market share. In this situation someone that would previously require a $250 deposit would be approved with no deposit.
It all comes down to their current debt vs. customer additions.