It really all depends on the NRD/NRS. For my OHARP experience (in the NYC area, though NRD headquarters is on Long Island/Garden City), after checking in at headquarters and meeting my immediate supervisor in charge who told me that I wasn't needed in the office, I phone mustered daily and had to take 2 people to MEPS. Some of my OCS classmates had to physically muster daily and were assigned tasks such as making sure that the office had the proper policies posted, etc. But some were even more hands-on than that.
Edit: had I lived closer to the NRD headquarters, I was told that I probably would have been required to physically muster every morning, though whether I'd actually have "work" to do after that isn't clear.