Transfer of DOI USGS TS to DoD Contractor

Asking as an FSO at a DoD Contractor. We recently hired someone who had an SSBI Investigation, granted Eligibility of Top Secret by DISCO in 2007, renewed upon PR in 2012 (case closed in early 2013). Since 2012 he transferred employment to the USGS which falls under the DOI. So far my RRU to transfer his TS back to us, as a DoD contractor, has not gone through. Any tips? This article was useful (https://news.clearancejobs.com/2017/03/18/department-interior-security-clearances/) but it only talks about reciprocity of DoD to DOI and I’m working the other way.