You don't need a lawyer to answer this question, only a little common sense.
A fanpage like on facebook is one thing, but using the specific sports team in the domain name can easily result in loss of your domain. That includes variations of the names.
You'll probably get away with something like this for awhile, but once the upper management at these times catches wind, you'll lose your domain pronto.
Especially if you are using their trademarks. However, to accomplish your goal doesn't really require those domain names does it? There are no laws against being a fan, or having a website dedicated to your favorite star/actress/sports-team. You just can't use trademarked names in appropriately.
Miami Heat = Miamihotness.com
Boston Celtice = BostonBBMachine.com
Why should your domain name require the actual sports team name? You can do everything needed in content/titles for SEO, and of course it would be better to have the trademarked terms in the domain title, but NOT necessary.
Hope that helps.