British Firm Go-Ahead has won the contract to operate 10% of Dublin Bus' route network.
The National Transport Authority announced four years ago that 23 were to be outsourced.
A new route is also being created as part of this new departure for Dublin transport.
It means the state retains ownership of the fleet but a private company will run the selected suburban routes (which don't travel into town) until the contract expires in 2019.
They include the 220 from Ballymun to Blanchardstown and the 75, Tallaght to Dun Laoghaire.
The NTA says it expects large numbers of new drivers will be hired by Go Ahead. Unions previously objected to the outsourcing plans over fears the move would lead to privatisation.
It had been expected they wouldn't oppose today's announcement after securing guarantees in labour talks in 2015.
However the National Bus and Rail Workers Union is warning of 'potential industrial flashpoints.'
General Secretary Dermot O'Leary says 'whilst accepting that an agreement was struck in 2015... it is nonetheless disappointing that Dublin Bus were unsuccessful in the so-called tendering process. It would appear that those alleged experts in the NTA and the Department have decided that workers’ rights are up for grabs and can be used, Dutch auction style, to help towards bidding for state contracts, the price of labour should not be used to win such contracts."
Full List of Routes
220 Ballymun to Blanchardstown
236 Blanchardstown Centre to Damastown
238 Tyrrelstown to Lady's Well Road
239 Blanchardstown Centre to Liffey Valley Shopping Centre
270 Blanchardstown Centre to Dunboyne
17a Blanchardstown Centre to Kilbarrack
76a Blanchardstown Centre to Tallaght
18 Palmerstown to Sandymount
17 Rialto to Blackrock
33a Swords to Balbriggan
33b Swords to Portrane
75 The Square Tallaght to Dún Laoghaire
76 Chapelizod to Tallaght
102 Sutton station to Dublin Airport
04 Clontarf Road to Santry
111 Loughlinstown Park to Dún Laoghaire
45a Dún Laoghaire to Ballywaltrim
59 Dún Laoghaire to Mackintosh Park
63 Dún Laoghaire to Kilternan
114 Ticknock to Blackrock Station
161 Dundrum Luas Station to Rockbrook
184 Bray Rail station to Newtownmountkennedy
185 Bray Railstation to Enniskerry