I've had no problems moving credit between BofA and FIA accounts. Recently I had 2 FIA accounts and applied for a BofA account. When I spoke to the credit analyst they extended additional credit AND were willing to distribute the total across the three cards any way I wanted, as long as I kept at least $5K on two of the cards that were visa signature.

I've done similar with Amex; moving credit from one account to another before closing.

A