The Aegis-owned Posterscope is set to enter a strategic buying deal with Interpublic Group's poster specialist IPM, under which both companies will share one buying and investment point.
The deal, which does not involve a merger, will take the agencies' combined share of the outdoor market to above 50 per cent.
Posterscope controls 42 per cent of the outdoor buying space and IPM - the third-largest specialist - has 12 to 14 per cent. The second-largest specialist is the WPP-owned Kinetic, with 40 per cent.
In the UK, IPM handles outdoor planning and buying for the clients of the IPG agencies Initiative and Universal McCann, as well as some direct clients, including BSkyB. This week it also emerged that Mike Cooper, the IPM managing director, is leaving to join Posterscope as its managing director in the US.
In August, IPM retained the £18 million outdoor media planning and buying account for Sky, with whom it has worked for the past five years, in a pitch against Kinetic.
The outdoor market is undergoing change, with the Publicis media arm VivaKi working on plans to launch its own outdoor specialist buying agency in markets across Europe (Campaign, 30 October).
The new strategy could include the UK, where outdoor buying for the Publicis networks, Starcom MediaVest Group and ZenithOptimedia, is handled through Kinetic and Posterscope, respectively.
Kevin Shute, the former sales director of the poster companies Mills & Allen and Van Wagner, has been working on the consultancy project for VivaKi, which could result in either closer alignment of VivaKi with Kinetic and Posterscope, or the launch of Publicis-owned services in the outdoor buying space.