A 1,000-tonne crane is being drafted in to lift the carriage, which was left hanging over an embankment.
However, engineers will have to ensure the crane can be safely supported by the adjacent A85 road – effectively a bridge on stilts over the northern edge of Loch Awe. It was built in 1972 when the road was upgraded.
Officials from nine government agencies and firms met yesterday to plan what Network Rail described as a "unique" task.
The front carriage of a two-car Glasgow-Oban train crashed over the edge of a 50ft embankment after hitting boulders on the line near Falls of Cruachan station on Sunday night. Eight of the 60 passengers were injured.
Several investigations have been launched. Network Rail said the hillside above the line was last inspected in April, with the track checked ten days before the derailment.
The rocks fell from below a Victorian-era trip-wire system that turns mechanical signals to danger if hit by rocks.
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Network Rail said the 1,000-tonne crane was expected to arrive at the scene from Carlisle today, with the lifting operation due to take place tomorrow. The front carriage will be moved on to a low-loader lorry. The rear carriage, which remains upright but above the track, will be lifted by the crane on to a rail wagon.
However, engineers have still to decide how to position the crane safely on the road.
The favoured option is to place it above a load-bearing "box" section of the road's support structure, which would take its weight. Alternatively, the crane could be placed on a thick platform to spread its weight evenly over a larger area.
It was not clear last night whether the road would also have to be strengthened. However, there is insufficient space beside the track for a rail crane to be used, while a helicopter has been ruled out because of the carriage's weight.
Repairs to the railway track will be required and the road cleared, with both routes expected to reopen by Monday.
Drivers have been forced to take a one-hour detour, either via the A82 through Glencoe, or the A83 via Lochgilphead.
Network Rail said: "This is a very complex operation. While we are committed to reopening the railway and road as soon as possible, the recovery work will last for several more days."
A spokesman for Transport Scotland said: "Partner organisations are working tirelessly in very challenging circumstances to restore road and rail links in Argyll as quickly as possible."
It has emerged the train's conductor was involved in a similar incident yards away 13 years ago. Angus MacColl, 54, was on board an Oban-Glasgow train whose front carriage was knocked off the track by fallen rocks in April 1997. None of the 40 passengers was injured.
A ScotRail spokesman said: "It is a remarkable coincidence a member of staff has been in a second traumatic incident. Our thoughts remain with him and all others who were involved."
Mr MacColl declined to comment.