Ultraraj,
Case transfers can happen for any number of reasons, and quite frankly they can even happen just at the discretion of the adjudicating officer, as a random check. read this:
{excerpt from the "I-485 Standard Operating Procedure", page 7-3.24}
Employment based Criteria
The adjudicating officer must determine whether the employment-based
I-485 meets waiver of interview criteria set forth below.
Employment-based:
• The principal applicant is employed by the same petitioner who submitted
the approved underlying employment-based visa petition.
• The principal applicant has been interviewed in the course of an
investigation or field examination, and the adjudicating examiner
determines that further interview of the applicant is unnecessary.
• The principal applicant has been approved as an alien of extraordinary
ability or alien of exceptional ability and is otherwise eligible for
adjustment of status.
• The principal applicant has been approved as an outstanding professor or
researcher, or a multinational executive/manager and has a continuing
offer of employment from the same petitioner who submitted the
underlying approved petition.
• Adjustment applicants who received national interest waivers based on
performing primary medical care to a medically under-served area must
demonstrate that they intend to continue according to the terms and
conditions of the underlying petition.
Deviation From Interview Waiver Criteria
The above interview waiver criteria may be modified by individual officers in
response to developing local circumstances and regional concerns, which
would dictate the need for further restrictions.
On a case by-case basis, an officer may choose to relocate an I-485 for
interview if he/she deems it necessary. Applications require a relocation if
the officer determines:
• a need for validation of identity
• a need for validation of legal status
• questionable admissibility and/or qualifications
• apparent fraud
• a second filing
• an applicant with fingerprint rejected twice
• an applicant with medical condition class A or B
• the A-file cannot be located at the time of adjudication.
