Telstra has confirmed the existence of Project Top Hat, its plan to make ADSL2+ services available to an additional 200,000 phone lines presently limited to just ADSL1 services, because there is no space in street-side cabinets to add ADSL2+ equipment. Telstra plan to rollout the upgrade by implementing an additional box on top of existing cabinets and will be available through both Telstra Retail and Wholesale customers. Telstra says:

In the past, to permanently increase the broadband capacity of a street side cabinet, we had to build another cabinet alongside the existing one. This could take months of planning and network construction.

Of course, the NBN is rolling out as we speak, but this new Top Hat roll out will let users who won't receive the NBN right away have access to ADSL2+ services. Details of the first 970 locations of the Top Hat upgrade can be found here.

Telstra is also upgrading backhaul from the street-side cabinets to Gigabit Ethernet to remove potential bottlenecks in the network. This work will take place over the next 18 months.