I have to amend my answer (sorry folks) after being reminded of a single important detail by Judge Pam Foust - DOI was prior to 2003, thus different rules. The following is the opinion of Judge Foust only, and is not the policy of the WCAB or DWC.

Liens must be filed prior to the execution of a C&R that is ultimately approved unless the defendant was on notice of the medical provider's claim prior to the C&R. For dates of injury before 1/1/03, if the defendant was on notice of the claim - i.e. the medical provider sent the bill to the insurance company and it either rejected the claim or remained silent and didn't do anything, or under other circumstances as set forth in the case law - I believe they can file the lien and seek to vacate the OAC&R up until 5 years after the date of injury. At that point, the WCAB loses jurisdiction to alter the OAC&R (or F&A) to make provision for the lien.

If the insurance company truly had no notice of the medical provider's claim prior to the C&R, I think the lien claimant is out the door no matter what the date of injury and there's case law on the subject. Once the security for the lien has been released, there are no funds against which the lien can attach and the ball game is over.

LC 4903.5 was supposed to limit a medical provider's right to file a lien; not expand on it. So I think the only way it changes the rules is that if the defendant was previously on notice of the medical provider's claim, the provider can file a lien within the time limits of LC 4903.5 without going to the trouble of vacating the OAC&R. If it means that the provider can file a post-C&R lien under any and all circumstances, that would mean that a defendant could enter into a global settlement for the purpose of laying the case to rest for once and for all, and yet unknown and unanticipated claims could still come crawling out of the woodwork after the settlement was finalized. I think that would be unconstitutional.

From Judge Foust's book on post-C&R liens:

section 2:54 Liens Filed Subsequent to Compromise and Release

Defendant is not liable for liens for medical treatment rendered after applicant's execution of a Compromise and Release that is ultimately approved by the WCJ, absent an express agreement to the contrary. (There is nothing preventing the parties from settling all issues except future medical treatment for a lump sum and concurrently stipulating that applicant is entitled to future medical treatment.) Neither is it liable for self-procured treatment that was rendered before the Compromise and Release was executed, if:

" No lien was filed until after the settlement was approved. [Permanente Medical group, Kaiser Foundation Hospital v. WCAB (Lennon) (1987) 52 CCC 220, writ denied];

" The parties were unaware of the lien rights and the lien claimant had prior notice of the pending workers' compensation case. [Lien Services of Northern California v. WCAB (Peterson) (1982) 47 CCC 427, writ denied.]; and

" The lien claimant was not misled by any false representation of the parties. [Kaiser Foundation Hospital/Permanente Medical Group v. WCAB (Orr) (1976) 41 CCC 614, writ denied.]

Mere mention in a medical report that the treatment costs were paid by a group carrier is insufficient notice to defendant to preserve the lien claimant's rights. [Blue Cross of California v. WCAB (Spratt) (1998) 63 CCC 55, writ denied.] However, in K-Mart v. WCAB (Acevedo) [(2003) 68 CCC 494, writ denied], the WCAB allowed the lien of a group medical carrier that paid for medical treatment provided by two hospitals in 1995 and 1996 in spite of the fact that the lien was not filed and served until approximately five months after the 1998 Compromise and Release. The Agreed Medical Examiner had stated in his report that he had reviewed lien claimant/hospitals' records relating to applicant and found the condition treated to be industrially caused. Spratt was specifically distinguished on the basis that while "there must be reasonable limitations on a defendant's obligation to track down the existence of remote medical providers," the references in this case were significant enough to impose a duty to investigate.

Normally, claims and amounts over which jurisdiction is not reserved in the Compromise and Release will be deemed denied by operation of law. [Labor Code section 5815.] However, if defendant was aware of the medical provider's claim for reimbursement prior to its execution of the Compromise and Release, the provider may be able to vacate the Order Approving Compromise and Release on the basis of fraud or another ground for the rescission of a contract. [Johnson v. WCAB (1970) 35 CCC 362, 2 Cal.3d 964.] In one case, an Appeals Board panel vacated an Order Approving Compromise and Release two years after the fact when the settlement incorrectly recited that defendant had paid all medical and hospital charges and the hospital, which had not filed a lien but which had billed the carrier and had received partial payment, was not served with a copy. [Sanchez v. TIG Ins. Group 23 CWCR 74 (1995), Appeals Board panel decision.] In another, the WCAB found that it had jurisdiction to consider medical treatment liens filed after the approval of a Compromise and Release based on the defendant's prior awareness of the claims as evidenced by the lien affidavit attached to the Compromise and Release and bills sent to the carrier. [Amcast Aerospace Products v. WCAB (Marquez (1999) 64 CCC 894, writ denied.]