As far as the area under fiber is concerned there shouldn't be any constraint on distance. Mostly TM lays fiber till the switch (the telekom box near your Taman) where the pizza box is fixed. The duty of the pizza box is to convert the signal from the copper wire into one compatible for fiber transmission. Hence the copper wire basically is from your house telephone set to the the TM switch which is a few hundred meters and hence the ADSL actually works only between your house and the TM switch. From the TM switch to the exchange is fiber all the way and fiber does not have the same characteristics as that of copper wire. You can transmit signals over long distances using fiber and you can have an optical amplifier at the end to boost the signal strength. Hence theoretically the distance restriction should be removed in the fiber areas. I am not sure why they stick to that distance restriction in areas of fiber.