One of the common methods—and it's not the only one by which departmental officials become aware of any changes in any kind of legislation—is through the system of broadcast messages, whereby the employees of the department who would be affected by changes to legislation are all advised of relevant changes to that legislation. Subsequently, offices of particular interest that have a very specific interest in that legislation would also be notified.
On June 19th, 2007. See this statement in context.