Incumbent Morrow Communications has worked with Translink since 2000 and intends to repitch. The three-year contract has the option of being extended by another year.
Translink is one of NI's largest companies, with a turnover in excess of £100m, and more than 3,500 staff.
In August, Translink's monopoly on NI's public transport was threatened when bids from private operators to run bus routes were invited. The first deal, signed last month, allows Chambers Coaches to run buses.
Punctuality data released last month by the General Consumer Council showed Translink's NI Railways met its punctuality target, but Ulsterbus and Metro had performed badly. One in ten of the latter's buses arrived more than seven minutes late.