I saw two updates over the weekend.
1. a merkin who does trains youtube stuff said that the "put a lid over central station and build tech-hub stuff on top" project has been canned due to heritage concerns.
2. The underground walkway from the upper level of Martin Place Station after the opal exit that used to drop you into either Martin Place or MLC Centre food court (now known as 29 Martin Place) has been re-opened with a new (cheap*) tiled surface. It is now half as long and just drops you into the Elizabeth St side of Sydney Metro exit. No signage yet, but it is basically a walkway to metro or a rainy day rat run to Castlereagh Street through Metro.
* It is in an improvement but looks like a cheap landlord bathroom, if you know what I mean. I assume will be re-done when Martin Place Station gets a makeover.