The business, which bills around £30m, will sit alongside outdoor buying for PHD's sister Omnicom shops OMD UK and Manning Gottlieb OMD at Posterscope.
PHD's account is moving after WPP acquired Poster Publicity to create Kinetic. PPL held a two-thirds stake in Outdoor Connection, with PHD owning one-third.
The deal is a boost to Posterscope, which has a 34% share of the outdoor market. This rose to more than 50% when it bought Alban in August, but it is set to lose MediaCom's outdoor buying to Kinetic.
Annie Rickard, the Posterscope chief executive, led the negotiations with Alban and has taken a place on its board.
Tess Alps, PHD's chairman, refused to comment.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the Forum.