Depends on who you ask.
For me as a Guide, the FOR is for sure the reference.
But...
Reality is...not even all Shuttle Companies follow the FOR rules.
On top, there are tons of tourists, that do not know about the FOR and their suggestions at all.
The Issallo side is in the best shape since years, because most people don´t ride em anymore, ´cause they have to pedal up.
The Bardineto thing has the same origin.. one owner of a fireroad said, he does not want Shuttles anymore(=they did not pay enough

) .