bk613 – I think that you are mixing up two different concepts, Hatzolah is by no means a DIY agency, they have the very same requirements that any other agency has. Their EMTs and Medics go to the same schools and colleges that any other EMT or Medic goes to. they have the same certification and license as well as the exact same continues education requirements that anyone else has.
Regarding the exposure argument, the average EMT and Medic in the 911 system does not do this full time, most 12 hour shifts see an average of 2 calls. Furthermore, a lot of 911 systems are not multi-tiered which means that if the caller gives a nature that would require paramedics, the medics will be dispatched and stuck with the transport, this is a waste of time and resources, this also means that some medics might have lower acuity calls their entire shift. This does not happen with most hatzolah systems.
Furthermore, most hatzolah systems are very busy and have high call volumes. divide these calls among the number of active members, this gives them a fair share of exposure.