nope..in delhi, nothing is done in the exchage. there is a specific dept at kidwai bhawan that determines/controls the speed policies ..exchange ppl only physically change the jumper settings to connect ur telephone line to DSLAM. After that they have no role.
But as I understand the modem needs to train with the DSLAM according to a line rate, say 256 kbps. This has to be changed in the local exchange DSLAM itself, isn't it so? Then that would be the peak speed we are capable of getting, provided the gateway at Kidwai Bhavan lets us have that speed.