In my response area, all volunteer firefighters are trained to the level of Firefighter-1, which is the same requirement to be hired as a seasonal firefighter. The department itself sends you to a condensed weekend academy, where, after 3 months, you do the test and get your cert. They then make you do in-house training to make sure you're able to use the local equipment and then they give you a pager and turnouts and send you to the fires. We're lucky in our backwater county that we have decent firefighting apparatus, with the newest vehicle being a 2010 International Watertender, which included air conditioning; something I've never seen in fire apparatus.
Our department is very fortunate. We always have a Captain on duty, and at least one Firefighter. In summertime, we have the Captain, 1 Engineer, and 2 Firefighters, and often the volunteers are on "Level 3 staffing" which means we get paid to man the fire station while the "Paid" guys are off doing stuff. Did I mention that regularly we get $7 per call? And the "Paid" guys cannot volunteer unless they meet their 900 hours of paid work for the season, which I believe is somewhere in the area of 9 months out of the year.
Now I'm rambling, but I think Volunteers are very important to a fire department. Short of privatizing the Fire Department, Volunteers are the most cost efficient way to deal.