Gigaset Communications GmbH, HMD Global Oy and Opera Software AS will be allowed to speak on behalf of Google in the case.
They will be joined by industry groups the Application Developers Alliance and the Computer & Communications Industry Association, the EU's General Court said.
CCIA backed the EU in a court battle with Microsoft over a decade ago.
The EU side will get support from German newspaper and magazine publishers, Czech search engine Seznam.cz AS, search firm Qwant SAS and the European consumers group BEUC.
