Johannesburg - The National Treasury's application to intervene in the urgent interdict to stop the launch of the e-tolling system was granted by the high court in Pretoria on Tuesday.
Judge Bill Prinsloo allowed the application because there was no objection from the opposition.
National Treasury would be the seventh respondent in the case.
It is arguing there would be serious implications for the future of roads and investment in public transport if the SA National Roads Agency Limited (Sanral) was interdicted from implementing the toll collection system.
Paul Kennedy, SC, was representing Cosatu as an observer.
"Cosatu is considering whether to become involved at a later stage," he told the court.
A total of eight lawyers and their juniors were in court representing both sides of the matter in the court application that was filed by the Opposition to Urban Tolling Alliance (Outa).