Hey Paul & Mary, I have quite the same experience as Mary's, with a client having also a 40 people call center, with the same representation mechanism.
Some years ago, we've had the case of 6 circles (having also sub-circles) doing the same work (during an implementation of a 450 people pilot in a 13 000 people company) and there was left to self-organizing - It did quite well but the experience lasted only 7 to 9 months before the parent corporation decided to stop Holacracy.
I would be happy to brainstorm with you, I am thinking of creating a sample circle that would serve as a model of all circles via a policy to be drafted. May be you've already tried that one!
With all my heart...