So what's the cost/benefit of this "green" bus?

From this article:

The conference, co-hosted by Cisco and the city and county of San Francisco, focused on what cities can do to reduce greenhouse gas emissions and encourage their residents to do the same. As an example of what might help, the city unveiled a "green" bus equipped with Wi-Fi and with screens that can tell riders where they are, when they'll reach their destination and how much they're reducing their greenhouse gases by taking the bus. That will encourage them to ride more often, the city said.
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Cisco isn't just pushing green technology to save money and the Earth. San Francisco's green bus, created by Cisco, is equipped with a Cisco router to link onboard Wi-Fi with outdoor 3G (third-generation) mobile data. Cisco also envisions the bus using its IPICS (Internet Protocol Interoperability and Collaboration System) technology, which unifies many public-sector radio technologies through an IP network.