The practice will be working as landscape designer under project leader Hawkins\Brown Architects and alongside London-based DSDHA.
Vogt will be taking forward the work done by global masterplanner EDAW, which has now left the project.
A Mayor of London spokeswoman said: ‘Following initial constraint identification, design analysis and urban planning, it was decided that EDAW’s masterplanning contribution was complete and that more emphasis needed to be placed on landscape design.
‘This was facilitated by the addition of Vogt to the urban-design team.’
Jason Prior, president of EDAW’s UK arm, explained that the firm’s work on the project was completed in November last year.
He said: ‘We surveyed the materials used on the square, the trees, and the positioning of the statues. The work also included assessments of the several requirements of the square, such as ceremonial routes and looking into the obvious security issues.’
According to Hawkins\Brown, the designs for the new-look square will be made available for public consultation in May, with a full planning application likely to be submitted in August.
The London-based firm saw off Foster + Partners to lead the redevelopment scheme – described by practice partner Roger Hawkins as ‘one of the most important squares in the world’.