Mahanagar Gas (MGL) on Friday signed an agreement to acquire rival private sector city gas distributor Unison Enviro from its promoters and existing shareholders Ashoka Buildcon and an investment fund managed by Morgan Stanley India Infrastructure, for an undisclosed sum. Unison Enviro is a subsidiary of highway developer Ashoka Buildcon and is into city gas distribution in the districts of Ratnagiri, Latur and Osmanabad in Maharashtra, and Chitradurga and Davanagere in Karnataka, to domestic, commercial, industrial and transport sectors.