Sample size of 1, but last year I completed an AA Gold Challenge in April, made Gold BIS in June, and made Plat in December.
Reading the AA board here on FT, it seems I'm in the great minority. Most of the folks posting there about the challenge do not seem to ever earn it the old fashioned way. But I'd guess FT is the exception, and the % of folks who earn the status after a comp or challenge is probably greater amongst non-FT'ers.