The answer gets a little complicated.
When Harry bought the WW&F assets in 1985, he bought about 60% of the right of way. Between that time and when he died in 2001, he would occasionally sell off a piece to an abutter, probably with an easement which would allow the railroad to come through.
Before he died, he deeded most of the right of way that he owned to the Wiscasset & Quebec Railroad Company - the same company that built the line in 1894 - which he had resurrected. Right of way that the Museum was operating on at the time he would deed over to the W&Q as well. The W&Q is a chartered railroad company, and (theoretically) has powers and rights that the WW&F Railway Museum does not have.
Harry also turned over a mile and a half of right of way to the WW&F Museum, the piece that goes up The Mountain and straddles 218 to behind Head Tide Church.
From what I understand, the W&Q has been researching what it is they actually own over the years. No map that I know of exists for the entire line. However, Alna's ownership is well established, and you can view the Alna tax maps which will show you what the W&Q owns.
Whitefield does not show the W&Q on its tax maps. I believe that Windsor does, but I can't recall if China does or not. I've not looked beyond that to know.