Thank you for your information.
The reason I asked that question is that one of my friends submitted 1-140 and I485 concurrently last August, got GC stamp on her passport at a local district of TSC yesterday. I inferred that may all I485 cases will be interviewed at a local district. If that is correct, it means that the process date of i-485 depends on the local office instead of service center. Otherwise I will accept a job offer in other service center, the TSC is too much slow in the case processing.