SF Bay's BART tube gets cellular ... almost

After months of complaining about 3G coverage on their iPhones, AT&T subscribers in San Francisco got some good news on Tuesday: Their mobile operator, along with Sprint Nextel, Verizon Wireless and T-Mobile USA, had extended their networks to the Transbay Tube, the underwater tunnel that Bay Area Rapid Transit (BART) subway trains take across San Francisco Bay.

The carriers had set up for service in the tunnel over the weekend, BART announced in a press release on Monday. It was an extension of service inside BART stations and tunnels across San Francisco, which the mobile operators have been gradually expanding over the past few years. The Transbay Tube is the key link of the whole subway system, carrying 160,900 riders across the bay to Oakland every weekday, according to BART.

However, a test of the service midday Tuesday showed that the Tube isn't ready for iPhones just yet. Though a reporter's iPhone 3GS achieved impressive speeds heading through downtown San Francisco on the subway, it started "Searching" on entering the tunnel and soon reported "No Service" until it emerged in Oakland a few minutes later. Customers of other carriers experienced only spotty service on Tuesday, according to a report by the San Francisco Chronicle.

AT&T is doing final testing and should have its Transbay Tube service up in a day or two, AT&T spokesman Mark Siegel said.

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