The organisations who are believed to be on the tender include: consultant engineers and planners Ove Arup and Partners; defence, transport and electronic fare system company Cubic Transportation Systems; facilities management and systems engineering company Serco; German rail company Db Rent and the Canadian company Société en commandite (Montreal).
The tender is divided into three parts: the installation of the bikes, the maintenance of them and the sponsorship of the scheme.
The winning bidder will be paid by TfL in the same way as a bus contractor and will not be able to generate revenue from ads.
A spokesman from TfL said: "TfL is still going through a confidential tendering process and will be announcing who the operator of the scheme will be in the summer."
On 10 March, Media Week revealed outdoor media owner JCDecaux, who runs the scheme in Paris, was not interested in the TfL tender.