We've been exchanging email with their Reseller Support and Sales departments; we don't have office phone lines installed because we don't provide phone-based support, and all our other communications are conducted online, so we eliminated office phone lines as an unnecessary expense.
The latest reply we got from them stated that their $99 setup fee is non-refundable, and that is clearly stated during their application process on their "review fees" page. However, they did mention something about making a "courtesy exception" in specific circumstances, which may account for why they offered you a refund of their "non-refundable" setup fee.
As you said, we cannot just "throw away a hundred bucks" that we never received in the first place and with no promises that we'd ever recoup it afterward, so we need Authorize.Net to verify how they will reimburse us if we pay for the refund they promised.
This situation is complicated by the fact that the only E-junkie personnel who have access to our company PayPal account and finances happen to be traveling abroad on a semi-working vacation at the moment. We Support staff would not be able to issue you a refund nor arrange for reimbursement from Authorize.Net, so we'd have to wait until next contact with our vacationing personnel to have them attend to this matter.
I hope you can understand how bizarre this situation seems to us -- first they take your payment for a fee which they state upfront is non-refundable, then they offer a refund anyway, but then they insist they cannot pay you the refund they offered, saying you should seek that refund from someone else (namely, us) who never received that fee in the first place, and we still haven't received any confirmation from them stating that they do actually expect us to issue their refund, let alone that they'll eventually reimburse us for that.