I've been thinking about the likelihood of this and I think on balance it is unlikely and, therefore, a tall tale. As such, it's entirely appropriate for this thread.
The terminal velocity for a human in free fall (the speed at which acceleration due to gravity balances with aerodynamic drag) is about 120mph, so any gust of wind capable of blowing someone off the viaduct, catching them, carrying them under an arch and depositing them back onto the deck must have been significantly stronger than this.