The case for acquisition went to a compensation court, and, upon paying the sum of 19,862 pounds 6 shillings and 6 pence, the Ohai Railway Board took control of the WR&CC line on 22 June 1917.
The trackage acquired from the WR&CC was built to the low standards of a bush tramway, unsatisfactory as a permanent line.
It could not even be appropriately extended into Ohai, though in 1919 an extension of 1 5/8 miles was opened to serve mines in the locality of Mossbank.
In 1918 a proposal to build a third line directly from Wairio to Ohai was made, and it included a small deviation through Morley Village, considered part of Nightcaps.
In June 2007, the Southland District Council adopted as part of the Otago Regional Land Transport Strategy a provision to upgrade the Ohai line and maintain it as a viable alternative to a road for bulk freight.
[3] After infrastructural upgrades such as a new rail load-out system were undertaken, the contract came into effect on 1 September 2008; to fulfil it, trainloads of up to 550 tonnes of coal leave the Branch daily.
[4] On 11 January 2021 a freight train of eight wagons each carrying two empty coal containers derailed at Wright's Bush between Thornbury and Makarewa; the track was expected by KiwiRail to take about a week to repair.
[5] Following the derailment it was announced that KiwiRail and Bathurst Resources had agreed $5.2 million would be spent on maintenance of the line, as well as track upgrades.