You cannot file I-140 in any shape of form, including expedited or not. Only an employer can. http://www.uscis.gov/forms/how-do-i-use-premium-processing-service. Give the link to the employer for information and advise them to hire an immigration attorney instead of relying on your posting on AVVO.
The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter,not should it be viewed as establishing an attorney client relationship of any kind.
Hopefully your employer has an attorney that can answer this question. USCIS.gov has information about premium processing and which forms can be filed through PP, EB3 140 is on the list. Your employer/attorney can request it, but you can't. You can however pay for the service.
Due to the nature of this forum, Attorney Maria J. Marty does not have all the information required to provide legal advice. Accordingly, her responses on Avvo are intended as general and not legal advice.