Of course they do. They're not going to sit by idly, are they? Not after claiming that they own all the patents. So, in order to prove this, they started a VP8 (WebM) patent pool. If you have a patent you think is infringed upon, they will help you sue.
http://www.mpegla.com/main/pid/vp8/default.aspx
I also see on the right that they are busy forming a LTE patent pool.
http://www.mpegla.com/main/pid/vp8/default.aspx
I also see on the right that they are busy forming a LTE patent pool.