If you don't mind using some command-line tomfoolery:
osascript -e 'tell application "Terminal" to activate' -e 'tell application "System Events" to tell process "Terminal" to keystroke "t" using command down'
This is from a stack overflow question on a similar topic.
If you want you can even create a new URL handler (or replace the ssh:// one) with a shell script as described at another stack overflow question.
EDIT1: you can get command line args from osascript by using something like the following (taken from the osascript man page):
on run argv
return "hello, " & item 1 of argv & "."
% osascript a.scpt world