HKL says it expects to sign a contract with the winning bidder by the end of November.
The project will be implemented using an alliance model based on a mutual contract between the two cities, the construction consortium, and the project design team, which comprises Ramboll Finland, Sito, and VR Track.
The double-track line will link Keilaniemi, Otaniemi and Leppävaara in Espoo with Haaga, Pakila, and Oulunkylä in northern Helsinki before terminating at Itäkeskus in the east.
The 33-station line will closely follow the route of Line 550, Helsinki's busiest bus line, with peak services operating at three-minute intervals.
The total budget for the line is €275m excluding rolling stock, with construction costs estimated to be between €205m and €225m.
Funding is being provided by the cities of Helsinki and Espoo and the Finnish government, which committed €84m to the project in April 2016.
HKL awarded Škoda Transportation’s Finnish subsidiary Transtech a contract to supply 29 Artic low-floor LRVs for the line in November 2016.
Construction is expected to begin in 2019.