In an address to the parliamentary committee on the National Broadband Network (NBN) in Sydney on Friday, CEO Mike Quigley said NBN Co remains "very comfortable" about staying within its forecast AU$34.7 billion capital cost to roll out the network.
Quigley said costs of the rollout and connections have also fallen significantly since the completion of initial connections.
Senator Ludlam said he's fairly pleased with NBN Co's progress so far.
He said the Greens support the federal government's current plan, and urged the Liberal Party to reconsider its broadband proposal.
"What I don't see today is any justification for the Coalition to swing a wrecking ball through current development," he told reporters on Friday.
The Coalition's analysis suggested that the NBN would not be completed until 2023.
Senator Ludlam said he is concerned that the construction timetable for NBN Co has fallen behind, and believes the company's risk management process needs to be improved.
The Coalition pitched an alternative broadband plan, which envisages a capital cost of AU$20.4 billion and a completion year of 2019.