However, the Globe and Mail report adds that a surge in iPhone sales in late June pulled the company's margin down to 38.5 %.

If that forecast turns out correct, AT&T "would be taking a hit..., and it sounds more dramatic than expected," said Joseph Bonner, an analyst at Argus Research Co. in New York. But "it's not really a bad thing," he said, meaning AT&T can count on the subscribers -- many of them won over from other carriers -- over a long-term.

One way AT&T could be hurt by the iPhone subsidies is if many subscribers suddenly back out of using AT&T after their two-year agreement for the iPhone runs out, Franklin said. "I doubt that's going to happen," he said.

"The short-term impact on earnings is a paradox," Franklin said. "The iPhone should create long-term value for AT&T."

Franklin acknowledged that iPhone's exclusive deal with AT&T is being studied by investors, partly to see how valuable an exclusive deal with a carrier subsidy can be to a carrier. AT&T has said it has a multi-year deal with Apple, but it is not clear when it ends.