The agreement, which has been reached before a supply and maintenance contract expected to be announced by the end of this month, means Auckland will own more electric trains than originally planned.
It replaces an earlier plan for the provision of just 38 three-car electric multiple unit (EMU) trains, to be supplemented by 12 electric locomotives which would have had to haul existing carriages on Auckland's southern railway line.
Mr Joyce said the package now agreed to would provide full electrification on all lines "so we have a single homogenous electric fleet right through the city and I think that's a very exciting result''.
He said ownership of its own fleet, with a new maintenance depot, would give the city greater independence "and it means passengers more importantly can look forward to faster and more reliable service''.
Mr Brown said the all-EMU fleet would cost less over its life-span than the original option and noted that Auckland had expected to pay the full bill through a regional fuel tax, rather than splitting the costs with the Government.
The Government through KiwiRail is also almost half way through electrifying and resignalling the rail network out to Papakura in the south and Swanson in the west for a further $500m.