Can the Govt "assume" a prime ktr's lease subcontract? If so, how?

Are you asking how to prevent it, or how to achieve it? If the later, there may be a way to effect a similar result. If the prime transfers all assets involved in the performance of the contract to the subcontractor, there may be a way for the government to recognize the subcontractor as the successor in interest on the contract. See FAR Subpart 42.12. The Government does not stand in the shoes of the prime, the sub does.

Thanks Jacques, FAR 42.12 was helpful. I am asking how to achieve it.

Is there any way to draft the contract at formation to "direct" or require the prime KTR to transfer all assets to the sub KTR etc, so that the sub KTR assumes the role of the prime KTR in the K with the Govt? My view is no, that would be the Govt interfering with a private contractual relationship, but I wonder if anyone has already encountered this dilemma and can shed more light on it.

If you are "draft[ing] the contract at formation," why not draft a contract with the so-called sub-contractor? It seems strange to want to draft a contract with a so-called prime contractor, with instructions in the contract for the prime contractor to give way to a so-called subcontractor during the course of contract performance.