Apparently it was really expensive to run a studio in Aussieland of that size after the tax subsidies and stuff went away.
Wasn't that long ago that Gearbox was suggesting 2K Australia was going to do a decent amount of those Borderlands "side-games" while they did other stuff since they had pushed the formula as far as they thought it could go. Though I see that Pitchford has recently stated that they know what to do for Borderlands 3 now.
2K consolidated their two Czech studios last year too. I had heard through the grapevine that after Irrational imploded they were looking at basically moving everything to 2K Marin (I think they had already moved some Australia and Czech staff there) with the Czech and China operations for outsourcing certain functions. Take Two's 2K HQ is in the same city and Visual Concepts is as well iirc. Plus Rockstar San Diego is in well, San Diego.
Looking at their recent releases it's all Rockstar's Massive Operation, Gearbox, Firaxis and Visual Concepts. Plus Evolve from Turtle Rock. And their mobile division Cat Daddy. It's like they're turning into Sega where three studios make everything that isn't their major brand.