Depending on the advertising used on a site, and the way in which you send bots out to the site - you could still be downloading the advertisers code. For example, if you sent out bots to a page using a browser control and proxy, you would end up downloading the sites content (+images, +javascript, etc) as well as the advertisers javascript code.
If the site uses a server side include form of advertising (e.g. advertising is displayed through a php/asp include ) - you would definitely end up affecting the CPC rate - regardless of whether you used a web control bot or any other type of bot.
Either way I don't see why anyone would want fake hits, it won't make your site any more popular (it's fake traffic, and its not going to increase your google rank/alexa rank), and its just going to eat your bandwidth (php/html whatever).