You will lose a few points (5-10) for the hard pull on a new account. After a year, you'll get them back; after two years, it'll fall off your CR.

Generically, if you BT with no new spend, your total debt is the same. The number of accounts with balances should stay the same, but for the first month or so until the BT happens there may be some overlap.

If the old and new accounts are both open, your total credit available will go up. This may reduce your utilization and may add a few points. If your current is 13K/13K and the new is 13k/26k You've cut your utilization from over 90% to 50%. 50% is not great, but far better than 90%. As you pay down, you'll hit 30%, then 9%, then 1%, all of which may bump your score.

The account closed after 12 months will stay on your report presumed with no negatives.

Not in your score: showing a $13K max balance paid off via the BT, may in the long run, make it appear to a credit analyst program that you can handle high balances. This is usually a plus and may effect future credit lines. A human looking at your CR might see the BT, but eventually the details may fall off so it looks like you handled a couple of high balances - the 1st account with the 13K and the account you BT'd to and paid off later.

Putting the old card in the sock drawer, if you can, may be a better option than cutting up the card or closing the account.

http://ficoforums.myfico.com/ gets more into this than FT. Since you are posting on FT, the questions are are usually:
and so forth.