Escheat would arise out of death, abandonment or dissolution of the owner of the property. An easement can arise by declarative action or will or it can arise by prescriptively (i.e. over 10 we used went over that path to get to school and the owner didn't say nuffin' so it became a public easement basically".) Eminent domain, of course, is exercise of sovereign prerogative to take property for a PUBLIC use. If METRO lacks actual authority they might rely on a kind of 'fast track prescriptive easement' that pretends to be eminent domain ("We are taking this....*waits* *waits* {no reply, no controversy} *takes") (fancy pants lis pendens). Adverse possession is a way of beating the state to perfecting an escheat which typically requires a seven year delay.
Crafty attorneys also attempt to promote encroachment activity restricted to a state's territorial jurisdiction by using prescriptive easements of a more abstract kind such as paying your local assessor to 'sell' the 'international building code' in his (sales) district--pegging it to the de jure local building code to give it an air of legitimacy and authority. A whale in the middle of the street just looks far out of place. Put it on a cart, in a see-through aquarium as part of a long-running, annual parade and then its "suddenly acceptable".