A and C
I don't see this as a goverment issue If the captain of the aircraft has reason to think that there is a bomb on the aircraft then he/she should order an evacuation.
As I read the original report - they would not let the pax off the a/c until they had the security staff to round them up onto a bus. Concern being that, if you pop the slides and everyone is milling on the tarmac, a suspect could run away. I am not saying that I agree with that but it is plausible
I sit to be corrected.