Uses a hacky workaroud to duplicate the frontmost Finder tab, since Apple hasn't provided great AppleScript support for this.

duplicateFinderTab.applescript

-- duplicateFinderTab.scpt
-- Uses a hacky workaroud to duplicate the frontmost Finder tab,
-- since Apple hasn't provided great AppleScript support for this.
-- Details at: 

on new_tab()
	tell application "System Events" to tell application process "Finder"
		set frontmost to true
		tell front menu bar to tell menu "File" to tell menu item "New Tab"
			perform action "AXPress"
		end tell
	end tell
end new_tab

on run {}
	tell application "Finder"
		if (count of Finder windows) > 0 then set duplicate_me to target of front Finder window
	end tell
	delay 0.5
	new_tab()
	tell application "Finder"
		set target of front Finder window to duplicate_me
	end tell
end run