No, it depends on each situation, many railroads did own their ROW free and clear. And even if there were 100-150 year old provisions to revert the land back to the original owners, the states still have the option of voided that through eminent domain. Far different than taking productive land through ED, unless the landowner had been receiving royalties from the RR (very rare.) The states can usually successfully argue that converting to a recreation trail fits under the "Health, Safety, and Welfare" provision, as walking/biking/skating on a public trail ostensibly promotes good health.
That's precisely the argument they used successfully in Missouri.
Carolyn