It’s one of the most talked, analysed, and potentially controversial corporate takeovers we’re ever likely to see, and it has rankled South Africa’s corporate watchdogs. Bloomberg today reports:

BHP Billiton which has made a $142 billion hostile bid for Rio Tinto Group, was subpoenaed by South African antitrust regulators to provide information it declined to give relating to the biggest mining takeover.

“I can confirm that we subpoenaed BHP in order to supply us with documents they were resisting to do,” Competition Commissioner Shan Ramburuth said in a phone interview from Pretoria, South Africa today. BHP is “challenging” the subpoena, he said, declining to elaborate on the type of information he sought.

The takeover may raise competition concern for the global supply of iron ore, Australia’s antitrust regulator said Aug. 22. European Union antitrust regulators widened a probe of the proposal last month, saying they have “serious doubts” about the combination. The deal will boost BHP’s control over commodities including iron ore at a time when they’re trading near record prices.

This raises the question of just what BHP isn’t willing to tell South African regulators, and whether our ACCC has been asking the right questions, or just rolling over?

The ACCC on Friday revealed it had reduced its concerns about the proposed BHP bid for Rio to questions about iron ore; and they didn’t seem all that serious.

And, if BHP isn’t being full and frank with regulators in South Africa (where the Milliton company was based and still has large operations), will the European regulators take not and ask them anyway?

It raises the question: what has BHP to hide, and why go to court to prevent the questions being raised and the information provided?