Making it work in non-html files would be a good bit of work, however from first glance the syntax of the tags looks close enough to smarty for that to work for the HTML part. You could just duplicate the html syntax file and change a few lines (namely the file extensions captured and renaming smarty to EE). Might not be perfect but it will get you a lot closer pretty quick. (Make sure to make a new language file from within TextMate so it gets a unique scope)