Insurance Australia Group, with brands such as NRMA, Swann and CGU, is setting up at Hume ready for processing while Suncorp, which has brands such as AAMI, Apia, Shannons and Bingle, is already pumping cars through its Fyshwick operation.

Once the Canberra storm event was categorised as "catastrophic" and the huge volume of claims was identified, the major insurers switched to an established fast-track process using specialist contractors to manage high volumes and "triage" vehicles.

It is estimated that more than 25,000 cars have been damaged and most are still waiting insurance assessment following the January 20 hailstorm which swept in through the outer suburbs and Belconnen, across the Acton Peninsula, into Barton then on to Fyshwick.

Although the full extent of the losses are not yet fully established, the Insurance Council of Australia estimated the repair bill across three states at $320 million. Canberra took the brunt of the storm impact.

Hail damage to cars is the most significant contributor to repair costs, with 12,000 vehicles waiting on assessment by IAG alone.

Hundreds of cars have already been "written off" as total losses by the insurance companies. Holding yards in Fyshwick, Hume and Mitchell are already overloaded and new holding areas are being set up on Majura Road to manage the overflow.

Once vehicle trucking companies are able to manage the enormous workload, most total loss cars will be trucked out of Canberra to auction houses such as Pickles at Belmore, in Sydney, and Mannheims, in Moorebank, and sold as salvage.

Some car insurers such as Suncorp have their own dismantlers and will absorb written-off cars into their network.

To some insurers like Suncorp, the underbody frames, mechanical parts, suspension and chassis components of late model hail-damaged cars are recycled into their repair networks to reduce cost.

Dave Wilkes, Insurance Australia Group's executive manager of motor assessing in NSW and the ACT, said that storm events such as Canberra experienced last month are not uncommon across the country and processes are well-established to ensure customers get the help they need.

"While this was certainly a big storm event by Canberra standards, a storm in Sydney last year produced probably as much vehicle damage and in Victoria in 2017, there were about 20,000 cars damaged," he said.

"As an insurer, we are ready for these extreme events and have people who can mobilise quickly; companies like Smart Repair and Bears which have their gear packed into containers and can basically set up and get going within a week."

A small proportion of affected cars have been written off already with hundreds now sitting in exposed yards at Fyshwick and Hume. These are generally those cars which have had windows smashed and water has entered the cabin.

Ron Duff, a retired assessor for AAMI, said that extensive water entry to the cabin is often be a catalyst for an insurance total loss on the car.

"If you have extensive panel damage already and then the glass is broken and water gets into the car, this can have a knock-on effect on damage to upholstery, electronics, and computers," Mr Duff said.

"Depending on the age and value of the car, this is when the cost of repair starts to become uneconomic."

IAG, which has the NRMA, CGU and Swann brands, has established two fast-track fast-track assessment centres in Hume while Suncorp, which includes AAMI, Bingle, APIA, Shannons and Bingle, have set up another in Fyshwick.

IAG has engaged the Wollongong-based Bears and NSW Central Coast company Smart Repair, while arch-rival Suncorp has contracted Gold Coast-based Wizard Automotive.

Once up to speed, both assessment centres will process hundreds of cars a day through an on-line system where customers are given a text message with the time of their booking and can wait while their car is wheeled through the process.

Some of the mobile systems used here for the first time are state-of-the-art technology. Smart Repair has brought in a $500,000 three-dimensional scanner which the car is driven through in walking pace, while photographed in high definition at 450 frames a second.

Mr Wilkes said that IAG's two temporary processing centres in Hume can manage around 300 cars a day each. He hoped the two centres will work through the outstanding vehicle claims within five to six weeks.

"Insurers work in a number of different ways; some will do paintless dent repair on site, get customers to come back later, or farm the work out to their authorised repair network," he said.

"Our operations will be fully equipped to do everything, from paintless dent repair to full paint and panel repair; they will have spray paint booths set up on site in the next week or two, ready for go."