Could the Charging Bull itself be viewed as an advertising campaign for the sculptor? After all, he was hoping to sell it and a few to various cities: http://www.nydailynews.com/archives/news/rock-solid-article-...
The same goes for the bull. If he had a plaque on it with his name, an artist statement, and some information to contact him, the piece wouldn't have had such an impact.
Arguable though.
The corporation and the marketing firm didn't make Fearless Girl, Kristen Visbal did.