Some school bus companies are filing a lawsuit to give the red light to a plan that will cut school bus routes in the Bronx and the rest of the city.Ten school bus companies say if the Department of Education's plan goes through, thousands of kids will be stranded in the dead of winter because their buses never showed up. The new plan required students eligible for bus service to register for it, but only 63,000 children were registered after the first deadline. The bus companies say they service about 10,000 more students each day. The companies filed a restraining order Thursday, claiming the new plan will create mass chaos in early December and January when it takes effect. The group also says companies will have to lay off 270 workers.A spokesman for Schools Chancellor Joel Klein says the bus companies would sooner have the Department of Education pay for empty bus seats than use the money in classrooms.