More definitive...from the 8-A instructions: "(d) If this form is used for the registration of a class of securities under Section 12(g), it shall become effective: (1) If a class of securities is not concurrently being registered under the Securities Act, upon the filing of the Form 8-A with the Commission.
IMO, no. I read it to say that if the 8-A was filed in tandem with a Securities ACT registration(like an SB-2 etc) then it would be effective immediately.