I am not aware of any exemption for performing the escrow analysis. What RESPA does say is that when you have a past due borrower, you can't necessarily go after them for a deficient (below $0) amount, like RESPA spells out in §1024.17(f)(5). Instead, RESPA defers to your mortgage agreement, which should comply with your state's laws. Here's what RESPA technically says:
These provisions regarding deficiencies apply if the borrower is current at the time of the escrow account analysis. A borrower is current if the servicer receives the borrower's payments within 30 days of the payment due date. If the servicer does not receive the borrower's payment within 30 days of the payment due date, then the servicer may recover the deficiency pursuant to the terms of the mortgage loan documents. [§1024.17(f)(4)(iii)]