Yes, approved and still valid PERM or a PERM application pending for over a year can, unless withdrawn, be used by another attorney to seek extention of your H1B beyond six years in the genuine change of employer context.
Please see below:
http://myattorneyusa.com/immigration-law-and-practice/nonimmigrant-visas/work-visas/extending-h1b-status-beyond-the-6-year-statutory-limit
Answered on Aug 27th, 2015 at 2:47 PM