This response is based on the information provided.  We suggest you discuss with your contracting team, program manager as appropriate. 

We are not aware of any new FAR/DFARS language regarding Mobilization-demobilization.  As to CLIN structure that is the purview of the contracting officer.  We need to put the applicable clauses on contract.  Based on the details of your specific acquisition, our contracting officer would use DFARS 252.236-7003 Payment for Mobilization and Preparatory Work or 252.236-7004 Payment for Mobilization and Demobilization as prescribed in 236.570 (b)(2).

It is possible USACE has adjusted its processes with regard to Mobilization-demobilization, so you may want to discuss this with your contracting officer.