Nortel Networks Corp. announced today a number of developments with its Provider Backbone Transport (PBT) carrier Ethernet solution. In addition to announcing that three new carriers have opted to implement Nortel's PBT system, the Toronto-based telecommunications equipment maker added new capabilities to PBT and added new members to its carrier Ethernet ecosystem. Switzerland's group-e, Highland Telephone Cooperative of Tennessee and the Gulf Coast's Southern Light are the latest carriers to jump on Nortel's PBT bandwagon.