It's entirely dependant on the exchange and what DSLAM cards it holds. I think it used to work that 4Mbps sync was handled by 4Mbps cards. I think it's just what's available now.
Thanks for the reply, this makes sense. When I am on a 10mbps connection things work relatively well and I can reach stable speeds up to about 6mbps; on a 4mbps connection I have a bad overall experience and rarely exceed 2mbps. Solution I guess is to upgrade to a 10mbps bundle, or go for a capped bundle.
