EHS Brann already worked on the WAGN account, while the c2c and Silverlink business was held by Publicis.
The agency's new contract begins on 1 April. It has been briefed to develop integrated work across all Londonlines brands, including radio and press ads, a customer relationship programme, promotions at stations, online activity and all ongoing customer communication.
The activity will initially target commuters but will extend to include campaigns aimed at leisure travellers.
David Hamilton, the commercial director at Londonlines, said: "EHS Brann has proved that it understands the challenges we face as a business and that it can deliver totally integrated solutions with an intelligent use of the database and strong creative."
Philippa Marlow, a board account director at EHS Brann, said: "This is a massive vote of confidence in the agency and in particular the team on the WAGN account."