O2 is going to have all its 4G related support from BT. And BT will help this operator achieve a faster network in near future.
O2 and BT have signed a contract for next ten years of support and co-operation. O2 will help BT develop a superfast network.
This agreement simply means that from now on BT will provide O2 all 4G services and it will help O2 get better and wider network capacity. BT has more secure spectrum in the 4G auction and it is in all potential for bringing in better services for network provider.
Additionally, BT will stay responsible for bringing O2 better back up and stronger connection between the network base station and the new network.