I have to say, I no longer believe a) , I used to. Its just too easy to blame 'fat fingers' or some other stupidity for a valuable test of where the populous mindset is should it be real. Will they panic? will they call authorities like they should? will they meet with other members of their militia? How does this stress test the phone systems? etc.
You can see it in the 'fat finger' stock market problem a while back, the 'drills' when the very scenario is being played out, and Bush reading an upside down children's book on 9-11. Now you see it here in the 'just happen to have filmed it all in the warning building just before it happened' scenario, and the delay in informing the public it was in fact a drill. Its like a weird 'plausible deniability' due to incompetence.
I believe they are playing us for fools again and again, whilst they build up a belief in us that they are incompetent so when the hammer falls they shrug and say they need better 'systems' in place. Then they go about removing more of our freedoms.
This is just a newer version of the 'war of the worlds' radio program. I bet the Lab technicians are rubbing their hands in glee at the data they were able to gain from this little experiment.
b and c for me, but if b and we do put it together, there are ways to deal with that too.