One of the more appealing features in warrants is that you have a longer period of time to give the underlying company a chance to appreciate before putting your money in.  With this thought, they may be privy to a watershed event and are choosing to get the shares now.

Another thought is that warrants are affected when a company is sold, and I can't swear to this, but I think in POET's warrant terms, POET is required to give advance notice to of a merger/acquisition so that they can make their best decision with all of the facts regarding whether to exercise, or not.

POET also has a large shelf offering and possibly that is earmarked for something specific which would require POET to inform the warrant holder.

Not trying to predict anything here, but only considering possibilities.