Think north of $15 million to re/build the line in? Way north - try $30 million!
Unfortunately, the value of Eastport's natural depth lies solely in one area, that being marketing/PR fodder. If bulk product ever did start moving through Eastport, it would move in Handy-size vessels... that draw ~30-ft. Big whoop. Eastport has never been, and most likely never will be a strategic deep-water port. It's too far off the grid for just about everything.
A Google-map scan of the port facilities is also telling. It's on an extremely small footprint with no room for significant expansion. Scroll west ~120 miles to Searsport. Not so deep, but deep enough and room to grow. Now scroll east from Eastport about 60 miles and look at Saint John's port complex. Wow!