Brunswick partner Jonathan Glass is acting for Autostrade, while partner Rurik Ingram is representing Abertis. The agency was brought in last week by both companies.
It is not the first time Brunswick has 'double-dipped' to represent both sides of a major merger. Its work for both sides of the £8.8bn Abbey/Grupo Santander merger prompted a furore in some City circles over a perceived conflict of interest.
Brunswick worked with Abertis in 2004 when it bought TBI, the company which ran Luton Airport. Abertis has ambitious plans for the airport, planning to triple its size by 2030 and add a new runway and terminal in time for the 2012 London Olympics. The firm also owns Cardiff and Belfast airports, and plans to extend both sites.
Only three weeks ago Abertis announced it had completed the takeover of French motorway firm Sanef.
Despite its acquisitive ambitions, the new company when formed is not expected to enter into a bidding war with Spanish rival Ferrovial for Heathrow and Gatwick operator British Airports Authority – but may snap up assets if they are put up for sale as a result of a takeover.
Abertis/Autostrade would also become Europe's biggest motorway operator, as the infrastructure sector goes through a strong period of consolidation.
The CEOs of Abertis and Autostrade will alternate leadership of the new firm with Salvador Aleamany, chief executive of Abertis, holding the top post first.