"Deprecated" means that those talkgroups are no longer in regular use by that agency.
Edisto Island public safety agencies use talkgroups on the Palmetto P25 system, instead of the Palmetto 800 system like the rest of Colleton County. I have just listed these talkgroups to the Palmetto P25 page. There is a tower site for Palmetto P25 located on Edisto Island for coverage. Other listeners have reported very poor Palmetto 800 coverage at Edisto.
Hope that helps.