The Basque Regional Government has agreed with the Provincial Council of Bizkaia on the financing and construction of metro line 4 in Bilbao with an initial budget of EUR 412 million. The regional government will cover 55% of the costs and the province of Bizkaia 45%, with the provincial contribution capped at EUR 200 million until 2032. The 6.7 km line is set to run from Matiko to Rekalde, connecting the southern districts of the city. An interchange with lines 1 and 2 will be built in Moyua. Construction in Rekalde is scheduled to begin at the end of 2027. Regional infrastructure operator Euskal Trenbide Sarea is responsible for the project. Furthermore, both sides agreed to seek the transfer of the metre-gauge infrastructure of the C4 suburban rail line from Adif to the region. The operator for line C4 between Bilbao, La Concordia and La Calzada was already transferred to the Basque regional government in 2025, whilst the infrastructure remains under central government control. In a second phase, the project aims to use line C4 for a metro extension beyond Rekalde towards Enkarterri.