Yes, it depends on how they're filtering. There's different p2p filters out there for a start. They seem to be applying a bandwidth shaper which works by giving priority to net surfing, but for p2p, it gets a lower priority. For eg, they may have it set to give 90% bandwidth to surfing & remainder for p2p which is probably a lot of people. http://www.logisense.com/tm_p2p.html
Here's an example of how shaping can be set up: http://titan.iwu.edu/~it/Policies/ShaperPolicies.html