Might be worth a quick visit to the Australian Government Takeovers Panel website and check on the 'creep rule'... ie acquisition of no more than 3% every 6 months once over 20%. If my interpretation is correct, NST can creep their holding by that much through on market purchases without obligation to launch a takeover. Whether they'd bother is another matter entirely.
EAR Price at posting:
20.5¢ Sentiment: Buy Disclosure: Held