its just an idle threat to get icasa to change their minds. if telkom should pull the plug, that would put thousands of people out of a job. not like they cared about firing people in the past, but this would leave only their executives to run their business. additionally, it would affect all ISP's revenues dramatically. telkom would then probably face legal action from every single ISP for abusing its monopoly status, as well as thousands of complaints from adsl users.
bottom line - it would cause too much chaos both financially and socially. the courts wouldn't hear of it, there's no way telkom would be allowed to cut the service. thats just abuse of power simply because they can't have things their way. telkom are just bluffing, stirring a storm in a teacup