When I worked at C-MED all the tones were generated from a programmable Zetron encoder. Technically VEMS was a quick call tone but it has since changed. I know the beginning tone has been made longer since there was problems hitting the Oxford based medic's radio to set off the pager. As for the the tone out frequencies, I could not tell you what they are.
Are you using a new Bearcat scanner with the tone outs?