OPM handing over existing clearance to other agencies

Wondering if anyone has any insight on how well OPM works with providing other agencies with an existing clearance?

My current T5 (only about a year old) was sponsored by OPM but my new job is going to be requesting the file in order what all they need/want to do in terms of bringing my clearance up to date before I can start with them.

The FSO has explained that the timeline directly relates to what/how much/if OPM decides to release my previous investigation, and when.

Has anyone been in a similar situation and have any insight as to how cooperative OPM might (or might not) be with this new agency?