The following comments are based on my discussions with several dealer reps in GA and AL, and some good old fashion hard work - R E S E A R C H !!
First, there are three types of discounts from MB that should be of interest to potential CLA buyers.
Fleet Employee Program
This Program is for employees of companies that participate in the Mercedes-Benz Corporate Fleet Program. Employees have the unique opportunity to do the same.
Executive Allowance Program
This Executive Allowance Bonus Program extends discounts and more to executives currently receiving vehicle allowances as part of their compensation package. The Executive Allowance Bonus Program is tailored for these select individuals.
Premier Access Program
Through an authorized participating dealer network, Mercedes-Benz Fleet Operations partners with various associations, offering full fleet incentives via a modified version of the Executive Allowance Bonus Program to members in good standing. Such organizations include, but are not limited to, USAA, American Dental Assn., American Bar Assn., American Medical Assn., some credit unions (e.g., Pentagon Federal Credit Union), and many others.
Second, the discounts vary according to the respective program. Regarding the "Fleet"-related discounts, you should be able to get from MSRP to Dealer Invoice price. For the other "Access"-type discounts, the amount of the discount comes off the negotiated price. Which means you negotiate your price FIRST, and afterwards you apply the discount.
Third, any discount should apply to any level of CLA. If you look at my previous post on this thread, the one about MB Announce Fleet Discounts, the announcement shows a $1000 discount for CLA (all), which means for all levels of CLA.
Hope this answers some questions.