Location: USA
At this moment, it is widely reported that the curent president has ordered cabinet secretaries and executive department heads to not participate in any transition activities with the apparent(*) next president. The apparent next vice president is currently a sitting senator from California.
As a sitting senator, could she ask (with an expectation that they would comply) for a briefing from each of those secretaries and agency heads? (**)
*To avoid argument about semantics, no one is the officially the next president until the EC votes are cast and counted. It is clear he will get enough votes from enough states.
**To avoid trivial answers, I know anyone can ask for anything. I did not want to say demand. Somewhere on the ask-summon-demand spectrum. I am also aware that the Senate is in GOP control, so she cannot get relevant committee chairmen to subpoena them.