"Fiber and bandwidth to cell sites are the most significant investments for mobile broadband, but they are booked to wireline," Butler said. AT&T does not publicly break out backhaul spending from other investments in its wireline network.

TownHall's Hallaren said that to make a fair comparison with Verizon's wireless spending, he had to leave out capital investment in backhaul because neither carrier reveals its backhaul investment. If wireless backhaul investments were as big a part of wireline spending as AT&T implied, the company would have to disclose that in regulatory filings, he said.

According to PCWorld's , conducted by Novarum, AT&T came in last place for reliability behind Verizon and Sprint in all 13 cities tested, tying with Verizon in just one location, Boston. However, its mobile download speed beat the other two carriers in two cities -- Boston and Phoenix -- and its upload speed led the pack in 10 of the sites. Two cities where it did not were the places where AT&T has faced its most intense criticism, San Francisco and New York City.

Analysts at investment bank Piper Jaffray found last month that AT&T's iPhone beat Verizon's Motorola Droid in download speed in six out of nine cities. Continuing problems in the high-profile San Francisco and New York markets affected the carrier's reputation, according to Piper Jaffray. "AT&T's network is finally starting to show the investments the company is making and performance is improving," the analysts wrote.

Real or perceived weakness in its wireless network doesn't appear to have hurt AT&T's business. In the third quarter ended last September, the company reported it gained 2 million wireless subscribers, a record for that part of the year, to end the period with 81.6 million. The churn, or turnover, among its postpaid subscribers was 1.17 percent, also a record for a third quarter, AT&T said. Meanwhile, its wireless data revenue grew 33.6 percent to $3.6 billion. The company's 1.6 percent drop in overall revenue was caused by declines in other businesses, such as wireline voice and directories.