Can a corp have more than 1 'Chairman Hiro' rezzed at the same time?
Chairman Hiro is a unique asset (there is a diamond next to the card name designating this status).  While multiple unique cards may be installed simultaneously, only one may be rezzed at a time.

So, if you have two Chairman Hiro's installed, and one is rezzed and the runner runs on it, you could conceivably rez the second Hiro which would cause the first one to trash itself before the runner accesses it (so long as you do this during a legal paid ability window).