If it's pretty much green fields all the way then that suggests there's not much demand for development, so not much would be made by selling off the old route.Probably not cheaper, but certainly feasible. Very little infrastructure in the way, pretty much green fields all the way from Chester to the outskirts of Crewe.
And as has been discussed already, the alternative - retrofit to OHLE would be relatively difficult and expensive for the few miles involved. Also the cost of a new ROW could be offset by selling off the old one for development. And a new ROW would be cheaper to maintain than the old one.