While awaiting a response from someone local, you could try monitoring the CMED/Emerg Medical Services freqs.
UHF CMED 4-10 seem to be the most common ones used for dispatch.
The problem in trying to receive the ambulances is that the channels are usually don't have repeaters. Hospital is on the 463.xx freq. and is usually strong since it has an antenna on the roof of a multistory hospital. The ambulance will be a weak signal on the matching 468.xx freq. and you probably won't hear it unless you are within a couple of miles.
We still have the EMSCOM or MEDS channels on our radios. However we use cell phones now because of the availability of them, security ( with all the concern about HIPPA) and ease of use. MEDS is used as backups in emergency.