Is A Practising CMA is Liable to Write GSTP exam?

As per proviso in Rule 83
Provided that no person enrolled as a goods and services tax practitioner shall be eligible to remain enrolled unless he passes such examination conducted at such periods and by such authority as may be notified by the Commissioner on the recommendations of the Council:

For latest update on exams plz refer Notification 60/2018 CT

Oh. That Means rights of conducting exams are in the hands of commissioner it seems.
I saw a Notification where Exams announced Only for existing Existing VAT Practitioners but no where they mentioned for CMA OR CA PRACTICING MEMBERS
Could you please analyse if there is estimated date ?

7th Dec 2018 is the exam date, portal for registration will open from 16th nov...

ok .. So All are allowed to register there .

Correct ...........