to answer my own question and for assistance of others....
you can convert up to a max of 50,000 AP miles at a time to Esso.
you can, however, do immediate subsequent transfers of 50K. so i did 50,000, 50,000 and 30,000 in about two minutes.
so now I have an additional 134,000 BA miles that cost me only $850 bucks from an account i had access to.
BTW, anyone know who pays for the transfers? it really costs me nothing netting out....AP, or Esso or RBC or BA? or all of them.