Question: When did the Australian rail freight operator, whose main commodities included Aluminium oxide, become part of QR National?

Context paragraphs:
Mainline Freight: Mainline Freight was a trainload rail freight operator based in Islington, London, England with operations extending to Yorkshire in the north and Somerset in the west.  It was formed from part of British Rail's Trainload Freight division as part of the privatisation of British Rail.

Aurizon: Aurizon Holdings Limited is a publicly listed rail freight company in Australia.  Formerly owned by the Government of Queensland, its assets were transferred to a new company, QR National Limited, in July 2010 in preparation for it being floated on the Australian Securities Exchange in November 2010.  Aurizon is Australia's largest rail freight company.

Aluminium oxide: Aluminium oxide (British English) or aluminum oxide (American English) is a chemical compound of aluminium and oxygen with the chemical formula Al O .  It is the most commonly occurring of several aluminium oxides, and specifically identified as aluminium(III) oxide.  It is commonly called alumina, and may also be called aloxide, aloxite, or alundum depending on particular forms or applications.  It occurs naturally in its crystalline polymorphic phase α-AlO as the mineral corundum, varieties of which form the precious gemstones ruby and sapphire.  AlO is significant in its use to produce aluminium metal, as an abrasive owing to its hardness, and as a refractory material owing to its high melting point.

Australian Railroad Group: Australian Railroad Group (ARG) was an Australian rail freight operator.  It began operations in Western Australia on 17 December 2000 following its purchase of the Westrail freight business.  It was purchased by QR National in June 2006.  The main commodities hauled by ARG included grain, mineral sands, alumina, bauxite, coal, woodchips, quartz, nickel and iron ore around Western Australia.  In June 2011 it ceased trading as a separate brand, and became part of QR National.

Transrail Freight: Transrail was a trainload rail freight operator based in St Blazey, England, UK with a large operating area including Scotland, Wales and the west of England.  It was formed in 1994 from part of British Rail's Trainload Freight division, as part of the privatisation of British Rail.

Regional Rail Logistics: Regional Rail Logistics is a rail freight operator based in New South Wales, Australia.  They operate containerised freight services three days a week between the Riverina towns of Junee and Cootamundra to Port Botany in Sydney, using rolling stock of Melbourne rail operator El Zorro.

Euro Cargo Rail: Euro Cargo Rail is a French rail freight operator formed in 2005 as a subsidiary of English Welsh & Scottish (EWS).

Public float of QR National: In 2010 the Queensland Government split the government owned rail operator Queensland Rail into two companies: the government owned passenger operator Queensland Rail and the freight operator QR National (now Aurizon), the latter to be floated in late 2010.

Interail: Interail was an Australian rail freight operator owned by QR National.  In June 2011 it ceased trading as a separate brand, and became part of QR National.

Genesee &amp; Wyoming Australia: Genesee & Wyoming Australia (GWA) is an Australian rail freight operator based in Adelaide, South Australia.  It is a subsidiary of Genesee & Wyoming and was formed in June 2006 to run the South Australian operations of the Australian Railroad Group.

Supporting paragraphs: Australian Railroad Group Aluminium oxide
Answer: June 2011