If it was the power issue, of course the crossover doesn't help, but as to bustitution, buses could still go to Dawson St. while trams shunt at the Zoo so that City bound passengers could have a better alternative of changing to a train at Royal Park.
Another doubt is that, with short terminations in place, FOC tend to make trams running to a different destination if network allows, so as to consume the unused running time so that the schedule of that run along the operational section remains the same. In this case trams on the south section were altered to travel to Moonee Ponds because the running time from Abbotsford St. to there is similar to that of going to West Coburg. I suppose trams in the north section operated to a limited service mode with immediate shunts regardless of schedule because there is no branch line there. The problem is, with some trams trapped in the north section, the available trams in the south section are not enough to cover the full schedule. A large gap will form at some stage. The south side might as well operate to a limited service mode with immediate shunt at Abbotsford St. so at least the frequency would remain consistent. Whenever services resume FOC could swap run cards so that whichever tram arriving at the terminus would represent the next scheduled run.
It reminds me of a water pipe burst near Belmont Ave. when route 109 was still operated by A class. Trams were shunted at Glenferrie Rd. Some drivers called FOC to ask what to do with the earliness. Those who did were instructed to run as route 42 to Elizabeth St., then as route 31 to Brunswick St., then run to Port Melbourne as route 109 so that the "folded" section of route would consume the unused running time between Glenferrie Rd. and Mont Albert. Those who didn't ask just drove straight to Port Melbourne. There were plenty of double shunting at Port Melbourne between those whose drivers asked for instructions and those who didn't. There were passengers who had less common sense than kindergarteners, who blamed drivers of trams at the end of shunt for not informing them that the double shunting tram was leaving first.