If these "agencies" are a part of your org and operating under your org's tax-exempt status,
you are correct.*
A non-profit cannot make a gift to itself, so they are really only making a budget transfer (cash) when they "purchase" tickets, or they are making the transfer of an asset when they "give" a GIK. Your accounting dept. should understand this and back you up.
However, if you really need documentation, I don't have it at my fingertips and also won't have the time to research it for a while. I did do a quick check of my CASE M&RS manual and didn't see it addressed, but I believe that's because it's understood that a non-profit can't make a gift to itself.
You might be able to quickly settle this by first talking to your accounting dept. If not, you could also check the archives at the
Fundsvcs.org website and/or post your question on the Fundsvcs listserv, where others might be able to direct you to the info you need.
* Disclaimer: I am not a tax attorney! This is just my $.02 worth - at least, I hope it's worth that much.
-