The agency is to handle as-yet-unspecified consumer PR projects, according to London Underground head of press and public affairs Claire Filby.
Bite - which pitched competitively in January for the contract and begun work last week - is the first external consumer PR consultancy that London Underground has brought on board in the past five years, according to Filby.
She said the 'good stories and good work (gets) lost against a very negative and political media agenda'.
In recent weeks the condition of the Tube network has come under fresh scrutiny, after a crash at Chancery Lane station in which 32 people were injured when a train jumped the tracks. The resulting closure of the Central Line has caused misery for beleaguered commuters.
Last month a London Assembly Tube scrutiny committee compared the passenger overcrowding on the Tube to 'cattle-truck standards', saying urgent action would be required when mayor Ken Livingstone takes control of the network in the spring.
At Bite the account is headed by consumer division head Susana de Santos, who declined to comment on the Tube contract, saying only that it was 'early days' and that projects had yet to be finalised.
In the early months of 2002, London Underground drafted in Financial Dynamics on a project basis to provide 'specialist advice' on City media, but that agency no longer works for LU, Filby confirmed.
Filby heads a 14-strong team, including seven press officers and four public affairs executives.