Please continue your questions on the same discussions in the same threads, MMN. I don't like repeating myself.
'To be going to' is an idiomatic future form, neither present progressive (which is another future form: 'I am helping you tomorrow morning') nor future progressive (which is yet another future form: 'I will be helping you tomorrow).
It does not apply to 'a top secret meeting is going on', which is not set in the future, but in the present. This is present progressive of the phrasal verb 'go on' (= 'occur').
I hope this helps.