Few years back, some ISPs started working on a model to establsh a layer-2 peering model with a central rack placed with any of the provider and have all the providers to connect their interfaces over switch as to peer with each other by exchaning their local routes. But somehow this remained as a conceptual thought and only few provider showed interest and PTCL being the only transit-provider at that time started markething PIE as the peering(so called) node as it used to be the transit point for all the internet traffic(ptcl being the only landing station at that time).
I dont think any of the ISP at this point offering peering at special rates rather, all the transit-carriers(PTCL,TWA etc) are pulling STMs with each other to localize the traffic which is not a true peering model.
I think to start, it more require a concensus among Service providers or efforts like Gaurab(Sanog Fame) to establish such node. This is a definite requirement and content localization is the key driver.