This report from TURN (The Utility Reform Network) has some excellent information about competition (and the lack of it) in wireline telephone markets, based on a study done in California. It is a lengthy report, but the Executive Summary does a good job of summarizing the findings. They key result was that there is still too little competition for phone service, and that for a variety of reasons, many households can't just drop wireline phone service and use cellphones--meaning that cellphone service is not an adequate market counterbalance to monopoly telephone service.