I read in several different forums and sites that they can do it. They don't actually just block ports; they snif the packets. I can connect with bittorrent and emule; I even get a "high id" indicating that all ports are connected; however whenever a transfer is started it is dropped immediatly. If I bring my pc down to the internet shop it all works fine.
http://www.google.com/search?q=isp+s...top+bittorrent