The firm's operations and maintenance division, Ascentis, will gain revenue of $A22 million for the first two years and a further $15 million for each year the plant is in operation.
Isaac Plains, an opencut operation, is 50:50 owned by Aquila and Brazilian miner Vale (formerly CVRD).
The Ascentis contract begins in mid January next year with forecast production for the first year at 1.8 million tonnes of coal, increasing to 3.8Mt in following years.
Ausenco managing director Zimi Meka said the project adds to the depth of operating experience and commodity diversification of the group.
"We are delighted to have been successful in being nominated as the preferred tenderer in this instance, as it brings together our emerging coal group and the strengths of our business - a comprehensive solution including a cost-effective and competitive approach, flexibility in our methodology and the experienced personnel in our Ascentis team," Meka said.