I believe it happened someplace on RJCorman's system, and recently someplace in upstate NY or that vicinity. But on the whole you're right - once a trail always a trail, and even if the RR gets put back in (there are those few rare occasions) there probably has to be a trail in the r/w which complicates ops/mtc a tad. Of course, most of the time the RR came out because it wasn't economic to have it there anymore; situations where that changes enough to justify reinstalling the RR are themselves quite rare.