BT has vowed to rip out much of its existing telecoms infrastructure by the end of the decade, as it pushes on with its 21st Century Network (21CN).
Speaking at the FT World Telecommunications Conference in London on Tuesday, Dr Paul Reynolds, chief executive of BT Wholesale, admitted that BT can't afford to run today's legacy equipment in parallel with new Internet Protocol-based infrastructure.
"People say to us, can't your PSTN equipment run for another fifteen years? Well, in pure engineering terms it can... but the cost and complexity of running legacy equipment alongside a new IP network will bust the business case for 21CN," said Reynolds.
Last year, BT announced that it plans to spend £10bn over the next few years to replace its existing Web of legacy networks with 21CN. While Reynolds painted an upbeat picture about 21CN and the new generation of IP-based services it will enable, the plan has alarmed some in the industry.
No telco of BT's size has attempted this kind of project before. When the plans were announced, some in the industry claimed that BT could be underestimating the challenge of being the first to combine equipment from different vendors in such a big commercial network.
21CN has also sparked concern that it could create a new digital divide, if the new services offered over 21CN are only available in urban areas.
Reynolds, though, insisted that the success of BT's ambitious project depends on universal coverage.
"The business model for 21CN is quite clear... you have to have IP everywhere," he said.