G'day Chinkerplonk,
Check out my blog entry about the
Hydro Hut on Windermere Plains. On that trip, I walked from the Overland Track just south of Waterfall Valley over the eastern Windermere Plains to a hydrographer's hut beside an unnamed tarn near Lake McRae. In the blog entry I talk about a 1919 mining map of the area which shows a track crossing the Forth River just north of the Wolfram Mines at Sloanes Bridge and zig zagging steeply up the Razorback, past Lake McRae and on to the Overland Track near Barn Bluff.
I'm not sure if this is the route spoken about by the walkers you met but it's a possibility. I have not been back to explore this area since my Hydro Hut walk but I have heard of people finding the old buttresses of Sloanes Bridge in the Forth Valley and heading up to the Barn Bluff mines from there. I think it may have been the North West Walking Club.
I should add that I don't imagine this would be an attractive alternative to the Overland Track. From Pelion Plains, you drop 600m down to the Wolfram Mines and then climb 700m up the Razorback. This is much bigger than any of the ups and downs along the OT! Other things to note are that the bridge at Old Pelion is completely rusted through and must not be trusted. Also, a number of posts on the forum refer to the gazillion trees over the track between Pelion Plains and the Wolfram Mines.
Best regards,
TasTrekker