If you want coffee real bad, they've got some real bad coffee.

YMMV, but from working an hourly job with an on-call component in MA I can tell you they make a distinction between two classes of 'On call'

Someone who is 'engaged to wait' on-site, like the firefighter analogy, is considered to be 'working' and therefore must be paid for their time.

Someone who is 'waiting to be engaged', but can otherwise go about their life as usual, is not working and therefore need not be paid. Once a call is made though they're on the clock for the hours spent dealing with the issue.

IANAL, and if you're taking your legal advice from Slashdot posts you really should have your head examined.

For those in MA, see http://www.lawlib.state.ma.us/subject/about/employmentfaq.html#oncall for ‘official’ info on the topic.

Nationally, the US Federal Fair Labor Standards Act has similar language, see http://labor-employment-law.lawyers.com/Pay-for-On-Call-Time.html