Yes, that should be possible. However, the Employer must be able to document the change of employment location by filing a Labor Condition Application (LCA) and even an amended petition if the situation warrants. An amended petition is required where there has been a "material change" in the nature of employment.
This change could affect your Green Card application if the location of work on the ETA 9089 happens to be the client location in State X, or even the Petitioner's work location in State Y. The ETA 9089 must carry proper endorsements to allow for travel.