A federal judge denied a request by several unions to halt Metra’s COVID-19 vaccine mandate, holding that the dispute is subject to mandatory arbitration and there is a strong public interest in transit employees being vaccinated.U.S. District Judge Matthew F. Kennelly of the Northern District of Illinois denied the unions’ request for preliminary injunction, holding that the dispute is appropriately characterized as a minor dispute within the meaning of the Railway Labor Act and thus subject to mandatory …