In the past I have been able to interface CCBill with my own internal stuff much in the way you are describing.
I don't know anybody at IBill very well... but I can honestly say that the people at CCBill, from top to bottom, are the friendliest group anywhere. Choose who you like... but if you ask me CCBill is the best company out there, especially as a primary biller.
Contact Lange on ICQ, I'm sure he can assist! #144268948 or you can email him at
[email protected]
Cheers!
Brad