Since you are BTing to an existing card, your overall util won't change, so the only effect on your score might come from the individual util.
Currently
Card #1: $2461 / $5450 = 45%
Card #2: $470 / $7000 = 7%
After BT
Card #1: $0 / $5450 = 0%
Card#2: $2931 / $7000 = 42%
Your individual util doesn't change much from this BT. I don't see much of an affect on your scores at all. The only thing I would caution you about is doing a BT to a card that currently has a balance @ 21%. Your $250 monthly payments will be applied to the balance with the lowest APR first (meaning the BT balance), and your 21% balance will sit there and sit there, accruing finance charges at a very high rate. In the meantime, you'll never be able to touch that balance as long as you have some of the BT balance left. From your previous post, it seems like it's going to take you a while to pay off the BT balance. You don't want even a small balance accruing interest at the rate of 21% for months on end.
Can you pay off the $470 @ 21% before you do the BT? If you can do that, then it seems like an OK plan to me.
Also keep in mind that depending on when your CCs report, it's possible that the balance you BT'd might be double reported for a while (if the card you're BT'ing to reports sooner than the card you're BT'ing from), which might drop your scores temporarily, since FICO will think you're carrying that balance on two different cards.
