The latest phase will bring the total investment to over £10m.
Network Rail said the height and rural location made the repair a 'complex' job.
Network Rail says the first phase of the project to build stations and a new railway track will begin shortly.
Network Rail interim report published into crash that killed three people in August.
Engineers on site assessing impact of landslip between Lochailort and Glenfinnan.
High winds and sea spray are causing overhead electric wires to trip in North Ayrshire.