Anyone can file a re-examination request ex parte. The EFF have done this occasion, without an actual filed lawsuit from the Patent Assertion Entity(PAE="troll") but it still costs thousands of dollars in fees and the EFF lawyers time.
On that point, how does the patent holder typically learn of cases of infringement? Would it be as simple as a surreptitious email? Or do you need something like a writeup in a publication, so they will see you as a potential goldmine?
I'm wondering what it would take to force a fight on crap patents - create something that infringes on a patent, contact the NPE through some untraceable channel to inform them, then await the lawsuit (or "licensing offer").