Setting the LendingImportAutoRush key in the Customization Manager to Yes instructs ILLiad to move requests containing the word "Rush" in the Service Level or Notes fields to Awaiting Rush Request Processing.
A Rush request will have "Rush" in the Service Level field of the Request Form even if "Rush" is not defined in your BillingServiceLevel table (in the ILLiad Customization Manager).
ILLiad will interpret "rush" and "RUSH" in the Service Level and Notes field correctly and move the request to Awaiting Rush Request Processing as intended.