Here in germany they do something similar. They allow the speed to peak at your max speed (1.7mB/s in my case) at the beginning of the download, then throttle it down after about 250KB to half your rated speed (.8mB/s in my case) and then finally fluctuate it every couple meg, allow it to peak at 3/4 of your full speed.
This is so predictable that I can guess where and when it's going to change. The worst effected apps are distributed server applications, like many p2p programs. I have a feeling that's what it's designed for. They also have a system in place that will block any port that has "too much" traffic going to or from it. We have no recourse, because one company still owns all of the infrastructure.