The exchanges are clustered around several high-population areas of the country, with Essex, South-East London, County Durham, Greater Manchester, South Wales and the West Midlands all in line for upgrades.
"Fibre is the future so we're speeding up the pace of our plans. We had aimed to get fibre to half a million homes by next March, but we're now being far more ambitious," said Steve Robertson, CEO of BT Openreach.
Two pilot locations, Muswell Hill in North London and Whitchurch in South Wales, went live earlier in the week.
However, BT has come under fire for deploying FTTC (fibre to the cabinet) in the majority of its upgrades. FTTC uses fibre-optic cable between the exchange to the street cabinet, with the so-called 'last mile' being run over copper wire. BT says this supports broadband speeds of up to 40Mb/s, potentially up to 60Mb/s.
The alternative to FTTC, FTTP (fibre to the premise), which replaces the entire connection all the way to the customer's property with fibre, allowing speeds of upwards of 100Mb/s.
A version of this story originally appeared on Microscope.