The winning bidder has been announced for the $2.14 billion privatisation of Adelaide's passenger train network.

The contract to run the city’s trains for the next 8 years has gone to Keolis Downer (KD) - a joint venture between the Downer Group and French transport company Keolis.

KD will take over from the end of January.

“Everyone will have a job at the end of this process,” Transport Minister Corey Wingard said.

“Train drivers will meet with Keolis and transfer over.

“Those that don't go over still have the option of working with the Government, and they'll be going through the redeployment program into other positions.”

Downer Group has previously been accused of using fake quotes attributed to government ministers in its bid to secure the contract.

A Keolis Downer spokesperson says the person that came up with the quotes never represented the KD venture.

The Rail, Tram and Bus Union (RTBU) says it still has questions about the “integrity of the privatisation process”, especially given that the current SA Government made several pre-election promises that it did not have a ‘privatisation agenda’.

“The public also needs to know if any extra sweeteners were thrown in to seal the deal with the new operator,” RTBU SA and Northern Territory branch secretary Daren Phillips said.

“This is a sad day for SA, but we will not give up fighting to protect jobs and protect services.”

There is also concern about Keolis' venture with UK infrastructure service provider, Amey, which was been fined millions of pounds by the Welsh Government over poor performance of its train operations.