Originally Posted by
hokiefyd
Yes, it's somewhat common with older bicycles, though I do think they typically used clamp-on or brazed-on cable guide "tracks" under which the bare inner cable would slide. This is the first one I've seen that uses short sections of cable housing over the bottom bracket shell. It seems to work well, but it does require a front derailer with an integrated cable stop, which is not necessarily very common, at least with modern derailers.
Yes, my 1985 Bridgestone 400 routed the rear derailleur cable above the bottom bracket just like that and it also came with a short section of housing covering the inside the braze-on guide.
The only downside to that routing became apparent when I switched the OEM 52T big chainring for a 46T. When I lowered the front derailleur to have the correct clearance the tail of the derailleur just cleared the cable. A smaller "big" chainring wouldn't have worked.