70% of our workforce (ambulance) here is volunteer but they only cover about 20% of the workload.
I do not have a "problem" with volunteers per-se as they willingly give up thier free time or work time to respond to calls; same with the volunteer firefighters; I do like the firefighters, they are bloody fantastic when you need them to turn a car into a convertible.
The issue with volunteers is there will always be a "compromise" between the people who go and seek to make paramedicine a career, put in thier 3 years to get the Bachelors Degree and work up to ALS level and the volunteers who are unable to commit to the same level of education. It's not because they don't want to outright but becaue they have other lives, jobs, families etc and can't spent the time required to learn in-depth anatomy and physiology, pharmacology, cardiology etc. They tend to operate at a lower clinical competency level and generally have fewer patient encounters.
New Zealand is branching out to seperate qualifications between volunteer and paid staff; those who want to make it a career will be expected to complete a Bachelors Degree (3 years) and a Post Grad Certificate in Intensive Care Paramedicine (Advanced Life Support - 12 months). The volunteer ambulance officers will be expected to complete a post-secondary, community college style, in-house Diploma in Ambulance Practice which is generally run over 12 months part-time.
This course contains substantially less theory in anatomy and physiology, cardiology and pharmacology than the old Certificate in Ambulance qualification it replaced. We used to do 6 assignments and two block courses of 6 days in class based mainly around A&P and cardio etc then a large on-road session to put theory into practice and be signed off as competent. This content was argued (by the volunteers mostly) to be too "theoretical" and "not relevant when crewing an ambulance" so a good portion of the micro-level stuff was taken out.
There is a vast disparity between what the Bachelors Degree staff and what the volunteers learn both in terms of theory and practical; the Degree core content is based around the common first semester cirricula for nurses, paramedics, physiotherapists etc whereas what the volunteers get (while I am impressed with it) is still inadequate and at a level that is "achievable" for them.
The US doesn't seem to have this problem as the education standards are the same, volunteer or paid, and they are inadequate as it is.