I do come across off terrain tyre tracks in several areas on the higher hills. Once saw a biker in the distance approaching Sgor Gaoith,,,,how the person arrived there I have no idea. I also met folks near the top of Mullach Clach a' Bhlair when coming out of Coire Garbhlach and when I talked to them on the summit about whether they cycled all the way up the Land Rover track they did say that a bit of pushing was done but as they said that the way back down on the track would be enjoyed.
As for the .912 top of the Corbett mentioned earlier I pushed my bike to the top after I reached the ruined wee shelter at the end of the bikeable track coming up from Glen Feshie and continued on my round trip of Minigaig, Bruar, Tilt , Bynach , Geldie and return to Kincraig down the Feshie.
I think that for battling the way to the Munro tops would need very strong legs....a bike with the 28 inch wheels? and deep pockets to keep up with the wear and tear on the bike.
My own use of the off road bike has been mainly for reaching the base of some of the higher hills by bike on the trails and tracks, to cycle two of the multi day walking paths and a few other of the round trips in the hills using paths and tracks.
Nowadays in my dotage I still enjoy being away from the busy roads on my bike doing shorter round trips on the walking ways that are on my doorstep. Only a couple of days ago when linking Feshie to the Corarnstilmore area the wee bridge that I used ten years ago had been removed?...it was only when I got to the relatively new bridge to Baileguish that I spotted the wee discs/arrow things with the Scotways indicating a path out to a crossing? close to the Baileguish ruin.
These re-organised paths need Scotway markers from both directions.