For most (all?) credit cards, the bonus is paid some amount of time after the statement closes. It's still "triggered" by meeting the spend; they just process it when they process the statement.

Also, I don't have much experience with BoA, but, with most card issuers, if you meet the minimum spend very close to the statement close date, the bonus miles won't post until after the NEXT statement. The definition of "very close" varies from bank to bank, and possibly even from card to card. In the rare case that I need the miles quickly, I usually try to plan it so that the spend posts (not is made, but actually posts) a week before the statement closes, which means that I try to get the spend done 10 days before. This is probably overkill for most cards, but I know that with my UA card (issued by Chase) I met the spend something like 5 days before the statement closed and I had to wait an extra month.