This is a sticky issue, with eminent domain not necessarily being the chief problem; the big problem obviously is right of way over private property. This is one of those fun hangovers from the middle ages, actually, when right-of-way was a sort of universal law. Ever since the enclosure movement in 18th century England lawsuits like these keep many a law firm in business.
In my favorite riding area the same thing happened: private property clashed with communal interest when the gov. had to convert all kinds of lines used for hauling coal ceased to operate when the mines closed. The solution was to weave sections of the tracks into signposted bike/hike/MUP trails, usually centred on an easily accessible spot with parking space. This way, there are some GREAT high speed gravel grinding sections in the MTB routes there!