As ZDNet points out, the Transport for London (TfL) authority ditched plans for a six-month feasibility trial due to the lack of any “credible” plans from mobile operators.

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But now it’s back on the table: the report says there’s a “near total mobile-coverage blackout over the Central London section of the London Underground, including even large stations”. Telcos should work with the London Mayor Boris Johnson to make it happen, according to report author Lord Carter - and the London 2012 Olympics is a good opportunity to do just that, so perhaps a service could be just three years away. The government says it will look at solving any regulatory barriers.

But the technical problems are another story: TfL has warned that some tunnels are very deep indeed and guaranteeing a minimum level of service is a tough challenge, and a very expensive one. And who will pay? TfL tell ZDNet: “We at the moment don’t have anyone coming to us with a commercially viable solution… if funding was found from external sources we would give consideration to how a system might be implemented on the Tube.”