Over the longer haul, 99% of the potential infrastructure value of the "destroyed" rail line is in the unified right of way ownership. Rails rust (or are sold for scrap, legally or not), ties rot, ballast (gravel) becomes choked with dirt, brush, and trees, and bridges and viaducts crumble. So long as the rail-to-trail project doesn't erect a too-high legal barrier to eventual higher-value uses, it's actually a best case scenario.