Alright, I just found the following:
Litigation
On the January 14, 2004, the Ninth Circuit U.S. Court of Appeals ruled that Playboy Enterprises Inc.'s (PEI) trademark terms "Playboy" and "Playmate" should be protected even in Internet searches that prompt pop-up advertisements. The suit originally started on April 15, 1999, when Playboy sued Excite Inc. and Netscape for trademark infringement. Attorneys Barry Felder, Catherine McGrath and Matthew Moren represented Playboy.
taken from:
http://en.wikipedia.org/wiki/Playboy
so yes, they have the term playmate trademarked as well as playboy
another informative article of value is at:
http://en.wikipedia.org/wiki/Playboy_Enterprises
I hope my topical post has been informative,
& viewed as being of some value, thank you.