I could be wrong, but it appears that you are confused about the difference between frequencies and talkgroup IDs. 853.275 is ONE of FIFTEEN freqs that are included in the Hillsborough EDACS system's east site. That particular freq is not "HCFR LZ Ops" as you referred to it as. You likely heard Aeromed activity on talkgroup ID 593, not activity on just one single frequency. If you parked your scanner on 853.275, you only heard a small portion of the entire conversation.