There is no separate template for the email that goes to the chair. It was originally just a CC of the confirmation email to let the chair know that someone had signed up. They get a copy of the exact message the person signing up gets.
There are already template tags for first name and last name and phone that will show the first and/or last name, as well as phone #, of the person who signed up. There is no template tag for the volunteer’s email, but the email is sent to the volunteer, so there was originally no need (they know their own email) and when set up as a simple CC email, the chair could also see the email it was sent to just by looking at the “to” email address.
There are also filter hooks already in place for the search and replace arrays to allow other plugins, or simple code snippets, to add to, or modify, the find/replace template/signup data used in the emails.