Red Bus has sold its transport business to Ritchies Transport Holdings for an undisclosed sum.
Sixty-three workers will lose their jobs as a result.
Red Bus Ltd chief executive Tony King said they are casual or fixed term employees - or have taken voluntary redundancy.
King said 145 staff will be transferred to Ritchies.
"Ritchies are a long-standing business for whom urban transport is their core activity.
"We believe they will make an excellent and committed owner for the business."
Workers have known since February that there would be downsizing after the loss of bus routes, he said,
Red Bus is fully owned by Christchurch City Holdings, which runs the council's businesses.
The company lost several contracts in the last round of the Environment Canterbury urban transport tenders announced in February this year.
