My background is contracting, so I highly encourage you to discuss this question with your legal advisor and cognizant property administrator as well.  However, based on my research, I did not find anything that indicated the DD Form 1149 (Requisition and Invoice/Shipping Document) equates to a Government admission the item was inspected/accepted by the Government.  It's a multi-purpose form used to document various transactions. The form only documents transactions; it does not authorize transactions.   Probably the most common use of the form is to document movement of government property between the contractor and the Government or from one physical location to another.  It can also serve as substantiating documentation of a receiving transaction for the accountable property officer who then updates the accountable property systems of record.  Moreover, DD Form 1149s cannot be used as authorization for the transfer of Government property from one contract to another.  DFARS PGI 245.103-71 provides guidance on the transfer of Government property.

For guidance on how the form was intended to be used on your contract, a good place to take a look would be in the performance work statement (PWS).  The PWS should also discuss the use of the DD Form 250 Material Inspection and Receiving Report which typically is the form used as evidence of government acceptance.  As a matter of fact, the DD Form 250 is the only form that should be used for documenting Government acceptance of contractor deliverables.  Typically, once an item is both inspected and accepted via a DD Form 250, it completes the contract terms and no longer has a performance requirement. 

Here's what FAR 46.501 says about acceptance:

                   Acceptance constitutes acknowledgment that the supplies or services

                   conform with applicable contract quality and quantity requirements,

                   except as provided in this subpart and subject to other terms ands conditions                        of the contract. Acceptance may take place before delivery, at the                     time of delivery, or after delivery, depending on the provisions of the terms                            and conditions of the contract. Supplies or services shall ordinarily not be                            accepted before completion of Government contract quality assurance                                actions (however, see 46.504). Acceptance shall ordinarilly be evidenced by                        execution of an acceptance certificate on an inspection or receiving report                            form or commercial shipping document/packing list.

Finally, what your contract (e.g. the clauses and PWS) says about inspection and acceptance is usually what ultimately governs.