Google has supported the idea of allowing multiple Webmaster Tools accounts to access the information from the same domain by using a separate meta tag for each account in the page header. This gets messy if you wanted to have any more than two accounts because how do you keep track of all that? I had forgotten how to implement this the other day, which was lucky because I discovered the process is now dramatically improved.
You simply click on the Verified link to the right of the domain name in Webmaster Tools and then add a user. So as long as the person you want to add has a Google account, you just enter their email address and you’re done. This is per domain, so if you only want to provide info for to one of many domains, no problem. For more details on how this works, see the article on the Official Google Webmaster Central blog.
Here’s an example of what it looks like: