The contract, potentially worth several hundred million pounds over the next five years, will support T-Mobile's growth plans and help avoid any investment risk in building out its own capability.
BT will connect T-Mobile's base stations to the central T-Mobile network. Leased lines will initially be used to connect these sites before an Ethernet-based service is introduced.
The new Ethernet service will further enhance the delivery of access and backhaul services to T-Mobile.
It will be designed and built to be fully compatible with BT's IP-based 21st Century Network (21CN), which BT is currently building across the UK.
It will also provide T-Mobile with the network capacity required to support future bandwidth hungry mobile services based on High Speed Downlink Packet Access technology. These include Mobile TV and music and video downloads.
Emin Gurdenli, technology director at T-Mobile said, "By partnering with BT we are able to achieve cost savings and focus on our core business, while BT takes care of our access backhaul requirements.
"This approach also means that we have the opportunity to control our future cost base more in line with business performance."
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