The big toll road operator Transurban has bought Brisbane's troubled Airportlink roadway for $2 billion - almost 60 per cent less than the original $4.8 billion construction cost.

Transurban won the auction run by toll road receivers PPB, acting on behalf of a syndicate of banks and opportunistic hedge funds which had snapped up tranches of cheap debt when the company was heading for administration.

To fund the deal in part, Transurban has announced it will raise $1 billion though a renounceable rights offering to its shareholders.

The entitlements are priced at $9.60 per share, a 5 per cent discount to Transurban's last traded price.

The 6.7 kilometre AirportlinkM7 tunnel connects Brisbane Airport with CBD was completed in July 2012.

Initial forecasts from the failed project operator - the Brisconnections consortium - that the Airportlink would attract 170,000 vehicles a day within months of opening proved wildly optimistic.

Fewer than 50,000 vehicles a day were using the tollway by the time it went into receivership in early 2013.

The Airportlink acquisition strengthens Transurban's position as the dominant player in Brisbane's toll road network, which includes Legacy Way and the Gateway and Logan Motorways.

It will also link up with the Clem7 Tunnel that Transurban and its partners purchased from the Queensland Motorways consortium last year for $7 billion.

Brisconnections' unhappy history

The deal rules off a very unhappy history for the Brisconnections consortium and its backers.

The consortium - put together by investment bank Macquarie Group and contractors Thiess and John Holland - won the right to build the tollway in 2008.

The heavy reliance on debt, financial engineering and use of equity from private - so-called "mums and investors" - led to one of the most controversial and calamitous floats in local market history.

A map showing Transurban's network in Brisbane. ( Supplied: Transurban )

On the first day of trading, the first $1 per share instalment in the $1.2 billion float lost 60 per cent of its value.

Within months, instalments were trading at 0.1 cents per share, the lowest possible price on the ASX.

Even before the price collapsed large institutional investors, who were becoming increasingly anxious about the GFC, bailed out, well aware of the damaging effects of debt and leverage in the financial environment.

The share price plummeted.

At the same time retail investors soaked up shares at what appeared to be a bargain price.

They were also often unaware that there was an obligation to buy two more $1 per share instalments down the track.

In 2009, more than 70 per cent of shares defaulted on the second instalment payment, prompting Brisconnections to sue and leaving many small investors facing financial ruin.

While Brisconnections - or "Bris Con" as it became known - relented on its small shareholders, the financial pressure on the company did not and several months after the tollway opened, it ceased trading on the ASX still mired at 0.1 cent per share.

The company collapsed owing its syndicate of 10 banks - led by the ANZ and including Macquarie, BNP Paribas, Soceite Generale and Allied Irish - $3.5 billion.

Transurban the logical buyer

Transurban and its partners were always considered the most logical buyer of the distressed asset, given the dominant position they enjoy in the Brisbane market and the possible synergies they could extract from the deal.

Transurban with 62.5 per cent of the deal was joined by its partners from the Clem7 acquisition, Australian Super which is footing 25 per cent and Tawreed Investments of Abu Dhabi with 12.5 per cent.

The group paid $1.87 billion for the tollway.

The Queensland Government will rake in stamp duty of $108 million, while lawyers and banks net the bulk $23 million transaction costs, bringing the deal's total cost to just over $2 billion.

The under-bidder was a consortium led by rival Australian infrastructure player CP2 as well as Dutch and Canadian investors.

Transurban chief executive Scott Charlton said the acquisition enhances the company's existing network in Brisbane and presents opportunities to drive efficiencies and increase earnings margins.

"The asset is performing well ... we have seen the earnings base lift following the key developments in recent months including the opening of Legacy Way and the removal of the majority of toll price discounts," Mr Charlton said.

The $1 billion rights issue follows last year's successful $2.7 billion capital raising at $6.75 to help fund Queensland Motorways purchase.