i'm no expert (not a check airman authorized to do fed rides), but i'll tell you about mine:
at my company, there are check airman authorized to do fed rides, so sometimes an actual fed does them, sometimes it's a company check airman. in my case, it was a company check airman. he did not ask any questions. he sat and observed. he checked all the paperwork. he debriefed me after it was over. it was very simple and straightforward. not a "checkride" mentality at all. i'd passed all the checkrides and had done enough ioe to have them do the fed ride, so he just wanted to see how i handled being a captain, i guess.
hopefully there are guys on here with more insight than i have, but i wanted to at least share my experience with you.