Telephone call pricing between telephone companies

Ever wonder how payments are regulated/arranged between phone companies when you call someone who is a customer of a different company?
FCC Scraps Vote on Controversial Phone-Rate Plan

"Mr. Martin had proposed to lower the rates phone carriers pay each other to transfer calls to almost nothing and allow companies that would lose money from the change to raise their monthly subscriber rates by as much as $1.50 for residential phone lines. Business increases would have gone as high as $2.50 per month.
The current phone-exchange payment system, which dates back to the breakup of the Bell system in 1984, is widely divergent, with some carriers charging a fraction of a penny per minute for outside calls to their customers and others charging hundreds of times that much for the same service.
The FCC has for years tried to reform the payment system, but policy makers and industry sectors can't agree on a solution."