If you look at the State Department October bulletin, they have stated that regression action will take place in early Jan 2005. This is expected to happen as USCIS and DOL are getting systems set up to clear backlog. This is no surprise or rumour. It is 100% expected to happen in Jan 2005 after Attorney Shustermann had a discussion with officials in Washington I believe three or 4 days ago. Regression is never a fair game. People who have filed their labor in 2001 and 2002 who are still waiting, this regression will be a godsend to them, as their cases will get processed. If you have filed your labor in 2003 and later, you will have a much longer wait. Priority dates come into play when regression kicks in.
Priority Dates determine when a foreign national will have the ability to file the final stage of the application for the green card (GC), known as the Adjustment of Status or I-485 application. The advantage of filing the I-485 at the earliest opportunity is that it allows the foreign national and any immediate family members the opportunity to file for the EAD or the employment authorization document (permission to work without having to maintain a temporary worker status such as H1B) and Advance Parole (permission to reenter the U.S. after travel abroad while the I-485 is pending). The priority date must also be considered for consular processing (CP) filings. A priority date, in an employment-based (EB) case requiring Labor Certification (LC), is the officially acknowledged date that the case was filed at the state level Department of Labor office, referred to as the SESA. If the EB case was filed in a category that does not require labor certification, then the priority date assigned by the INS is the date the I-140 (Immigrant Visa Petition) is received by the INS Service Center. If a person has already filed the I-485 application when the dates were current, but then the Visa Bulletin date retrogresses to a date before the priority date, the foreign national would still accrue the benefit of being able to remain in the U.S. with renewable EAD or work authorization and permission to travel, even after completing the six years on H1B status in the U.S. However, the I-485 could not be approved until the date again becomes "current."
Priority date for labor substitution cases will probably be the date that the labor was intially filed for the person that you are substituting for. But I am not 100% sure on it. Regression stinks!! But when you have too many applicants from a particular category and country and less number of green cards to be allocated, there is really nothing the State Department can do about it except switch to regression.