More than 680 drivers were issued with tickets for £30 after being diverted in Cathedral Street, on the day of the Great Scottish Run in 2012.
Some have refused to pay the fine and are locked in a legal battle.
A Glasgow City Council spokesman said: "The adjudicator stated the circumstances of this case are unique.
"She stated,'It is not beyond the realms of possibility that for a very short time, a person involved in stewarding or similar may, for a short period during the day, have directed traffic westwards along Cathedral Street instead of eastwards'.
"While we may not necessarily agree with this interpretation, we have accepted the adjudicator's decision."
City motorists have become increasingly angry at the city council's bus lane cameras.
Last week, the Evening Times exclusively revealed city council roads bosses had made a U-turn over fines for drivers who stray into bus lanes on Christmas Day and New Year's Day.
Enforcement cameras will be left on during these days - when there are no buses on the road - but will not issue fines.
The move follows an Evening Times campaign.
Fines of up to £60 were handed out to 370 drivers in the city, with cameras catching 147 people on Christmas Day and 223 on New Year's Day.
The council says the U-turn is part of a "pilot scheme" but one motoring expert called on officials to "just admit they got it wrong".
A council spokesman said: "Cameras will not be switched off but contraventions will not be enforced."
The city council has issued 231,168 tickets since they started using cameras in April 2012.