First of all, let's assume that Micros~1 is telling the truth, and that it really did do just what AT&T did.
Now that you have cleaned up the coffee that you blew through your nose guffawing at the previous statement...consider whether anyone raised a complaint of the AT&T action regarding lobbying Congress. If there was no complaint (e.g. everybody involved believed that this was "bizniz as usual"), then Justice would have no reason to prosecute. In this case, to quote a refrain from the '60s, "The whole world is watching", and any missteps Micros~1 makes are amplified. If the did something wrong (I should probably remove the "if" in the previous clause, but let's give them the benefit of the doubt for the purposes of this discussion) someone will file a complaint, and prosecution will follow.
Now, what was Ashhole's phone number again...?