Timmermans answered to my question that he’s ready to think twice about the best legal basis for a lobby transparency register to be mandatory for lobbyists and ready to question if the so far planned Interinstitutional Agreement is the best way. Agreements between EU-institutions can bind only employees but not lobbyists as outsiders. This openness is a positive signal from the Juncker-Commission.
During his visit in the Greens/EFA group, Frans Timmermans was asked by Sven Giegold about lobby transparency and the plans of the Juncker Commission. Here you can see the question and Timmerman’s answer: