BHP Billiton are very active with the accomodation globally at the moment.
They've just completed and moved into their new Perth office:
They're moving the HQ in Melbourne
http://171collins.com.au/171-collins/tower/
And now this Houston building... that's of cash floating about.
BHP's registered office for the ASX listed entity (BHP Billiton Ltd) is in Melbourne but the office which really is only head-office functions like Finance, Marketing and the CEO's office pales in comparison to the size of the offices in Perth & Brisbane where they're closer to all the mines.
They're heavily decentralised with a lot of their technology work done out of Singapore - Pretroleum in Houston and of course the LSE Entity (BHP Billiton Plc) office in London.