Hello:
I'll answer your last question first. Person A would have a better chance of getting accepted if he took the February OAT and therefore his file is essentially complete when he applies in August/September as compared to Person B who will perhaps get interviewed before scores for the October OAT are out in December but will be placed on conditional acceptance.
If Person A and Person B both took the October OAT and Person A applied in September and Person B applied in November, and OAT scores are the only things missing from each person's file, I THINK it will not matter who gets reviewed first. Unless I'm mistaken, schools receive a print out of scores from all applicants that listed on their OAT that they wanted the scores sent to that school. When the schools receive the scores in December, it is still relatively early in the application process so your chance for a seat is still good. I'm sure if the class size is quickly getting filled, they may consider that you did apply a bit early and it will almost depend on how early you can schedule the interview.
I think applying early really puts you ahead of the game, and especially if you have took the OAT before you applied.
Here is my timeline when I was applying, interviewing, and when I received my acceptance notification to give you an idea on what you might expect:
SCCO:
Applied 09/01/02
Interviewed 10/26/02 (First day of interviews)
Acceptance notification 10/28/02 (Yes, they are that quick with decisions)
SUNY:
Applied 08/01/02
Interviewed 10/21/02 (Dr. Johnston came to my undergraduate college)
Acceptance notification 11/01/02
ICO:
Applied 08/01/02
Interviewed 09/19/02
Acceptance notification 10/03/02
Newenco:
Applied 08/01/02
Interviewed 12/18/02
Acceptance notification 12/20/02
I didn't list Berkeley since they do not do rolling admissions.
I took the February OAT, and had all my letters of recommendation ready when I applied.
Best wishes,
Rosanna