I doubt Lake Jct was ever used for passenger transfer, unless there was something different going on there earlier, as there are no telegraph codes or any other note codes printed for Lake Jct. And at least from 1902, per the tables posted on here so far, it appears there was maybe only a switchman at the junction in 190x era - see the 's' note in the 1902 and 1908 tables. The letter 's' might mean something else entirely though. Maybe Mr. Ramsey could post the notes key for those pages here so we could see what all the notes were. I note .
What's more interesting to me (since I don't know much about operations there) is that it appears that most crews and engines for the Branch were based in Lake City, not Sapinero. Crews got up in the morning, made the run to Sapinero and turned engine and/or train and made the return to Lake City. As Ralph pointed out there's a disparity between MWF and TThS Branch times, but in the '32 Tables you can see the MWF trains met the WB mainline train and the TThS trains met the EB mainline train. Similar in earlier years? The other notable item is that there is a much longer layover in the 190x Tables at Sapinero for 356/357. It's possible in 1902 the home terminal for 359/358 (passenger train) was Sapinero, so one crew based at each terminal for the Branch, but it also may be that both were in Lake City with 356/359 being one (morning) job and 358/357 being the other (afternoon job). From a union perspective I'd guess the former. The longer layover may have been for mainline meets, but maybe there was also some switching to do in Sapinero for the 356/357?
Anyone know what the turning facilities were in Sapinero and Lake City? I have yet to find the val maps and 359/358 show a 5 minute arrival/departure at Lake City. The earlier Tables seem to say they had wyes (need that notes key).