I think you are correct; but Stagecoach and the various authorities had the use of one in 2007, for demonstration purposes, from Kirkcaldy Beach by the old Stagecoach/Fife garage, to Portobello Beach, by the Marine Gardens Garage of originally Edinburgh Corporation Buses, now Lothian Transport.
We travelled on it, from Kirkcaldy to Portobello, followed by LT bus to Princes Street, walked to St Andrew's Square Bus Station; and Stagecoach Fife bus over the FRB and back to Kirkcaldy - about 70 miles, free!
https://www.youtube.com/watch?v=zzqE1o4Rlng