I always had the impression that taking in-house call for fellows was an exception -- at most places that I know of they're home call. When I interviewed for PCCM no program that I looked at had in-house call during the ICU blocks. There was only one program I interviewed at that came close to being in-house -- it was still home call but the fellows were required to come in for every admission, so they usually stayed overnight anyway. That was a q4 call setup, though. Most people looking at that program seemed to think that this was a pretty unusual setup.
At my own program, we usually take q1 to q2 home call in both the SICU and MICU, and we rarely have to come in at night, unless we're in the SICU. This is also what the straight critical care fellows at our program do as well. We have off every other weekend while on a critical care rotation. In the SICU, if we need to come in for a significant portion of a night and we're on call the next day, there is a back-up fellow who will take that next call. If that happens in the MICU (which is much more unusual), usually the attending will offer to cover the next night.