The fountains were designed by WET Design, and was five times larger than anything they had ever done before. According to this article, "Bellagio's attraction consists of white lights, a fog system and four types of devices that shoot water into the air at varying heights. One of those devices -- basically robots called oarsmen -- is the only one that can make the water change directions." The exact cost isn't public knowledge, but it's estimated to be somewhere between $40-$75 million. To keep it up and running, there are approximately 30 engineers working every day. The engineers come from varying backgrounds, but all of them have dive training.
The equipment was specially invented and designed for the Bellagio fountains, so it's pretty unlikely that we see much of the same equipment used in our water and wastewater systems. But check out the pictures (I can't paste them here because of ownership issues) of the pumping equipment room, control room and panels here (click on the first picture to make it bigger and then click the arrow to make sure you view each of the seven pictures at the top of the article). Some of that sure looks familiar! I think we'd be right at home working on the Bellagio fountains. Except perhaps for those dive training requirements....
I also found the video below that talks about some of the specific technology that brings the show to life.
P.S. I just can't get enough of big water fountains. Check out this article to check out The Best Fountains in the World.