Mobile phone coverage on London's underground Tube network has always been a bit hit-and-miss. Whilst a good signal isn't out of the question coverage varies a lot and cannot be relied on. A mobile broadband signal (typically 3G or HDPA) is even harder to get and keep.
The British Government has pledged to help mobile broadband providers to increase the signal strength by 2012. The 2012 Olympics are aiming to be the most technically advanced Olympics yet and mobile broadband for spectators is part of that aim.
The Digital Britain Report has suggested that the forthcoming Olympics are a great reason for broadband operators and the city of London to work together for greater digital coverage. The technological no-how is currently up-to-date but the network systems need upgrading. The issue as usual is who will accept the costs: the government or the providers. If the providers foot the bill there will need to be profit in it for them.