Mid 2018 was the date they'll have to come to a new arrangement in regard timelines - the weather and permission delays in regard the MMP have seen them with an excuse but taking that into account the end of 2018 would see the start of production which IMO is unlikely.
I would think TAM would have a good hand in renegotiating an extension with NST who in the end would want to see production up and running themselves to increase and in some cases replace existing resources it has elsewhere - Newmont are doing very well at the Granites and Callie:
Tanami Expansion Project Adds Profitable Production and Extends Mine Life
08/31/2017
The project achieved commercial production safely and on schedule for the approved $120 million development capital investment.
The expansion is expected to increase Tanami’s annual gold production by 80,000 ounces per year to between 425,000 and 475,000 ounces of gold per year, lower all-in sustaining costs to between $700 and $750per ounce, and extend mine life by three years.
This expansion also creates a platform for further growth and studies to develop a second expansion are underway.
“Tanami’s team has more than doubled gold production while cutting costs by about two-thirds and significantly improving resource confidence since 2012. The expansion project continues this trajectory, offering robust returns of 35 percent at a $1,200 gold price,”
